Class: JSON::LD::API

Inherits:
Object
  • Object
show all
Includes:
Compact, Expand, Flatten, Frame, FromRDF, ToRDF
Defined in:
lib/json/ld/api.rb

Overview

A JSON-LD processor based on the JsonLdProcessor interface.

This API provides a clean mechanism that enables developers to convert JSON-LD data into a a variety of output formats that are easier to work with in various programming languages. If a JSON-LD API is provided in a programming environment, the entirety of the following API must be implemented.

Note that the API method signatures are somewhat different than what is specified, as the use of Futures and explicit callback parameters is not as relevant for Ruby-based interfaces.

See Also:

Author:

Defined Under Namespace

Classes: RemoteDocument

Constant Summary collapse

OPEN_OPTS =

Options used for open_file

{
  headers: {"Accept" => "application/ld+json, application/json"}
}

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Frame

#cleanup_preserve, #frame, #remove_dependents

Methods included from Utils

#add_value, #as_resource, #blank_node?, #compare_values, #has_property, #has_value, #index?, #list?, #node?, #node_reference?, #value?

Methods included from FromRDF

#from_statements

Methods included from Flatten

#create_node_map

Methods included from ToRDF

#graph_to_rdf, #node, #parse_list, #parse_object

Methods included from Compact

#compact

Methods included from Expand

#expand

Constructor Details

#initialize(input, context, options = {}) {|api| ... } ⇒ API

Initialize the API, reading in any document and setting global options

Parameters:

  • input (String, #read, Hash, Array)
  • context (String, #read, Hash, Array, JSON::LD::Context) —

    An external context to use additionally to the context embedded in input when expanding the input.

  • options (Hash{Symbol => Object}) (defaults to: {})

Options Hash (options):

  • :base (String, #to_s) —

    The Base IRI to use when expanding the document. This overrides the value of ‘input` if it is a IRI. If not specified and `input` is not an IRI, the base IRI defaults to the current document IRI if in a browser context, or the empty string if there is no document context. If not specified, and a base IRI is found from `input`, options will be modified with this value.

  • :compactArrays (Boolean) — default: true —

    If set to ‘true`, the JSON-LD processor replaces arrays with just one element with that element during compaction. If set to `false`, all arrays will remain arrays even if they have just one element.

  • :documentLoader (Proc) —

    The callback of the loader to be used to retrieve remote documents and contexts. If specified, it must be used to retrieve remote documents and contexts; otherwise, if not specified, the processor’s built-in loader must be used. See documentLoader for the method signature.

  • :expandContext (String, #read, Hash, Array, JSON::LD::Context) —

    A context that is used to initialize the active context when expanding a document.

  • :flatten (Boolean, String, RDF::URI) —

    If set to a value that is not ‘false`, the JSON-LD processor must modify the output of the Compaction Algorithm or the Expansion Algorithm by coalescing all properties associated with each subject via the Flattening Algorithm. The value of `flatten must` be either an IRI value representing the name of the graph to flatten, or `true`. If the value is `true`, then the first graph encountered in the input document is selected and flattened.

  • :processingMode (String) — default: "json-ld-1.0" —

    If set to “json-ld-1.0”, the JSON-LD processor must produce exactly the same results as the algorithms defined in this specification. If set to another value, the JSON-LD processor is allowed to extend or modify the algorithms defined in this specification to enable application-specific optimizations. The definition of such optimizations is beyond the scope of this specification and thus not defined. Consequently, different implementations may implement different optimizations. Developers must not define modes beginning with json-ld as they are reserved for future versions of this specification.

  • :produceGeneralizedRdf (String) — default: false —

    Unless the produce generalized RDF flag is set to true, RDF triples containing a blank node predicate are excluded from output.

  • :useNativeTypes (Boolean) — default: false —

    If set to ‘true`, the JSON-LD processor will use native datatypes for expression xsd:integer, xsd:boolean, and xsd:double values, otherwise, it will use the expanded form.

  • :useRdfType (Boolean) — default: false —

    If set to ‘true`, the JSON-LD processor will treat `rdf:type` like a normal property instead of using `@type`.

  • :rename_bnodes (Boolean) — default: true —

    Rename bnodes as part of expansion, or keep them the same.

  • :unique_bnodes (Boolean) — default: false —

    Use unique bnode identifiers, defaults to using the identifier which the node was originall initialized with (if any).

  • :simple_compact_iris (Boolean) — default: false —

    When compacting IRIs, do not use terms with expanded term definitions

  • :adapter (Symbol) —

    used with MultiJson

  • :validate (Boolean) —

    Validate input, if a string or readable object.

Yields:

  • (api)

Yield Parameters:

Raises:



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# File 'lib/json/ld/api.rb', line 89

def initialize(input, context, options = {}, &block)
  @options = {compactArrays: true, rename_bnodes: true}.merge!(options)
  @options[:validate] = true if @options[:processingMode] == "json-ld-1.0"
  @options[:documentLoader] ||= self.class.method(:documentLoader)
  @namer = options[:unique_bnodes] ? BlankNodeUniqer.new : (@options[:rename_bnodes] ? BlankNodeNamer.new("b") : BlankNodeMapper.new)

  # For context via Link header
  context_ref = nil

  @value = case input
  when Array, Hash then input.dup
  when IO, StringIO
    @options = {base: input.base_uri}.merge!(@options) if input.respond_to?(:base_uri)

    # if input impelements #links, attempt to get a contextUrl from that link
    content_type = input.respond_to?(:content_type) ? input.content_type : "application/json"
    context_ref = if content_type.start_with?('application/json') && input.respond_to?(:links)
      link = input.links.find_link(%w(rel http://www.w3.org/ns/json-ld#context))
      link.href if link
    end

    validate_input(input) if options[:validate]

    MultiJson.load(input.read, options)
  when String
    remote_doc = @options[:documentLoader].call(input, @options)

    @options = {base: remote_doc.documentUrl}.merge!(@options)
    context_ref = remote_doc.contextUrl

    case remote_doc.document
    when String
      validate_input(remote_doc.document) if options[:validate]
      MultiJson.load(remote_doc.document, options)
    else
      remote_doc.document
    end
  end

  # Update calling context :base option, if not defined
  options[:base] ||= @options[:base] if @options[:base]

  # If not provided, first use context from document, or from a Link header
  context ||= (@value['@context'] if @value.is_a?(Hash)) || context_ref
  @context = Context.new(@options)
  @context = @context.parse(context) if context
  
  if block_given?
    case block.arity
      when 0, -1 then instance_eval(&block)
      else block.call(self)
    end
  end
end

Instance Attribute Details

#context ⇒ JSON::LD::Context

Input evaluation context

Returns:



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# File 'lib/json/ld/api.rb', line 45

def context
  @context
end

#input ⇒ String, ...

Current input

Returns:

  • (String, #read, Hash, Array) 


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# File 'lib/json/ld/api.rb', line 40

attr_accessor :value

#namer ⇒ JSON::LD::BlankNodeNamer (readonly)

Current Blank Node Namer

Returns:



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# File 'lib/json/ld/api.rb', line 50

def namer
  @namer
end

#value ⇒ String, ...

Current input

Returns:

  • (String, #read, Hash, Array) 


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# File 'lib/json/ld/api.rb', line 40

def value
  @value
end

Class Method Details

.compact(input, context, options = {}) {|jsonld| ... } ⇒ Object, Hash

Compacts the given input according to the steps in the Compaction Algorithm. The input must be copied, compacted and returned if there are no errors. If the compaction fails, an appropirate exception must be thrown.

If no context is provided, the input document is compacted using the top-level context of the document

The resulting ‘Hash` is either returned or yielded, if a block is given.

Parameters:

  • input (String, #read, Hash, Array) —

    The JSON-LD object to copy and perform the compaction upon.

  • context (String, #read, Hash, Array, JSON::LD::Context) —

    The base context to use when compacting the input.

  • options (Hash{Symbol => Object}) (defaults to: {}) —

    See options in #initialize Other options passed to expand

Options Hash (options):

  • :expanded (Boolean) —

    Input is already expanded

Yields:

  • jsonld

Yield Parameters:

  • jsonld (Hash) —

    The compacted JSON-LD document

Yield Returns:

  • (Object) —

    returned object

Returns:

  • (Object, Hash) —

    If a block is given, the result of evaluating the block is returned, otherwise, the compacted JSON-LD document

Raises:

See Also:



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# File 'lib/json/ld/api.rb', line 201

def self.compact(input, context, options = {})
  expanded = result = nil

  # 1) Perform the Expansion Algorithm on the JSON-LD input.
  #    This removes any existing context to allow the given context to be cleanly applied.
  expanded = options[:expanded] ? input : API.expand(input, options)

  API.new(expanded, context, options) do
    debug(".compact") {"expanded input: #{expanded.to_json(JSON_STATE) rescue 'malformed json'}"}
    result = compact(value, nil)

    # xxx) Add the given context to the output
    ctx = self.context.serialize
    if result.is_a?(Array)
      kwgraph = self.context.compact_iri('@graph', vocab: true, quiet: true)
      result = result.empty? ? {} : {kwgraph => result}
    end
    result = ctx.merge(result) unless ctx.empty?
  end
  block_given? ? yield(result) : result
end

.documentLoader(url, options = {}) {|remote_document| ... } ⇒ Object, RemoteDocument

Default document loader.

Parameters:

  • url (RDF::URI, String)
  • options (Hash<Symbol => Object>) (defaults to: {})

Options Hash (options):

  • :validate (Boolean) —

    Allow only appropriate content types

Yields:

  • remote_document

Yield Parameters:

Yield Returns:

  • (Object) —

    returned object

Returns:

  • (Object, RemoteDocument) —

    If a block is given, the result of evaluating the block is returned, otherwise, the retrieved remote document and context information unless block given

Raises:



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# File 'lib/json/ld/api.rb', line 496

def self.documentLoader(url, options = {})
  options = OPEN_OPTS.merge(options)
  RDF::Util::File.open_file(url, options) do |remote_doc|
    content_type = remote_doc.content_type if remote_doc.respond_to?(:content_type)
    # If the passed input is a DOMString representing the IRI of a remote document, dereference it. If the retrieved document's content type is neither application/json, nor application/ld+json, nor any other media type using a +json suffix as defined in [RFC6839], reject the promise passing an loading document failed error.
    if content_type && options[:validate]
      main, sub = content_type.split("/")
      raise JSON::LD::JsonLdError::LoadingDocumentFailed, "content_type: #{content_type}" if
        main != 'application' ||
        sub !~ /^(.*\+)?json$/
    end

    # If the input has been retrieved, the response has an HTTP Link Header [RFC5988] using the http://www.w3.org/ns/json-ld#context link relation and a content type of application/json or any media type with a +json suffix as defined in [RFC6839] except application/ld+json, update the active context using the Context Processing algorithm, passing the context referenced in the HTTP Link Header as local context. The HTTP Link Header is ignored for documents served as application/ld+json If multiple HTTP Link Headers using the http://www.w3.org/ns/json-ld#context link relation are found, the promise is rejected with a JsonLdError whose code is set to multiple context link headers and processing is terminated.
    contextUrl = unless content_type.nil? || content_type.start_with?("application/ld+json")
      # Get context link(s)
      # Note, we can't simply use #find_link, as we need to detect multiple
      links = remote_doc.links.links.select do |link|
        link.attr_pairs.include?(%w(rel http://www.w3.org/ns/json-ld#context))
      end
      raise JSON::LD::JsonLdError::MultipleContextLinkHeaders,
        "expected at most 1 Link header with rel=jsonld:context, got #{links.length}" if links.length > 1
      Array(links.first).first
    end

    doc_uri = remote_doc.base_uri rescue url
    doc = RemoteDocument.new(doc_uri, remote_doc.read, contextUrl)
    block_given? ? yield(doc) : doc
  end
rescue IOError => e
  raise JSON::LD::JsonLdError::LoadingDocumentFailed, e.message
end

.expand(input, options = {}) {|jsonld| ... } ⇒ Object, Array<Hash>

Expands the given input according to the steps in the Expansion Algorithm. The input must be copied, expanded and returned if there are no errors. If the expansion fails, an appropriate exception must be thrown.

The resulting ‘Array` either returned or yielded

Parameters:

  • input (String, #read, Hash, Array) —

    The JSON-LD object to copy and perform the expansion upon.

  • options (Hash{Symbol => Object}) (defaults to: {}) —

    See options in #initialize

Yields:

  • jsonld

Yield Parameters:

  • jsonld (Array<Hash>) —

    The expanded JSON-LD document

Yield Returns:

  • (Object) —

    returned object

Returns:

  • (Object, Array<Hash>) —

    If a block is given, the result of evaluating the block is returned, otherwise, the expanded JSON-LD document

Raises:

See Also:



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# File 'lib/json/ld/api.rb', line 162

def self.expand(input, options = {})
  result = nil
  API.new(input, options[:expandContext], options) do |api|
    result = api.expand(api.value, nil, api.context)
  end

  # If, after the algorithm outlined above is run, the resulting element is an
  # JSON object with just a @graph property, element is set to the value of @graph's value.
  result = result['@graph'] if result.is_a?(Hash) && result.keys == %w(@graph)

  # Finally, if element is a JSON object, it is wrapped into an array.
  result = [result].compact unless result.is_a?(Array)
  block_given? ? yield(result) : result
end

.flatten(input, context, options = {}) {|jsonld| ... } ⇒ Object, Hash

This algorithm flattens an expanded JSON-LD document by collecting all properties of a node in a single JSON object and labeling all blank nodes with blank node identifiers. This resulting uniform shape of the document, may drastically simplify the code required to process JSON-LD data in certain applications.

The resulting ‘Array` is either returned, or yielded if a block is given.

Parameters:

  • input (String, #read, Hash, Array) —

    The JSON-LD object or array of JSON-LD objects to flatten or an IRI referencing the JSON-LD document to flatten.

  • context (String, #read, Hash, Array, JSON::LD::EvaluationContext) —

    An optional external context to use additionally to the context embedded in input when expanding the input.

  • options (Hash{Symbol => Object}) (defaults to: {}) —

    See options in #initialize Other options passed to expand

Options Hash (options):

  • :expanded (Boolean) —

    Input is already expanded

Yields:

  • jsonld

Yield Parameters:

  • jsonld (Hash) —

    The flattened JSON-LD document

Yield Returns:

  • (Object) —

    returned object

Returns:

  • (Object, Hash) —

    If a block is given, the result of evaluating the block is returned, otherwise, the flattened JSON-LD document

See Also:



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# File 'lib/json/ld/api.rb', line 243

def self.flatten(input, context, options = {})
  flattened = []

  # Expand input to simplify processing
  expanded_input = options[:expanded] ? input : API.expand(input, options)

  # Initialize input using
  API.new(expanded_input, context, options) do
    debug(".flatten") {"expanded input: #{value.to_json(JSON_STATE) rescue 'malformed json'}"}

    # Initialize node map to a JSON object consisting of a single member whose key is @default and whose value is an empty JSON object.
    graphs = {'@default' => {}}
    create_node_map(value, graphs)

    default_graph = graphs['@default']
    graphs.keys.kw_sort.reject {|k| k == '@default'}.each do |graph_name|
      graph = graphs[graph_name]
      entry = default_graph[graph_name] ||= {'@id' => graph_name}
      nodes = entry['@graph'] ||= []
      graph.keys.kw_sort.each do |id|
        nodes << graph[id] unless node_reference?(graph[id])
      end
    end
    default_graph.keys.kw_sort.each do |id|
      flattened << default_graph[id] unless node_reference?(default_graph[id])
    end

    if context && !flattened.empty?
      # Otherwise, return the result of compacting flattened according the Compaction algorithm passing context ensuring that the compaction result uses the @graph keyword (or its alias) at the top-level, even if the context is empty or if there is only one element to put in the @graph array. This ensures that the returned document has a deterministic structure.
      compacted = depth {compact(flattened, nil)}
      compacted = [compacted] unless compacted.is_a?(Array)
      kwgraph = self.context.compact_iri('@graph', quiet: true)
      flattened = self.context.serialize.merge(kwgraph => compacted)
    end
  end

  block_given? ? yield(flattened) : flattened
end

.frame(input, frame, options = {}) {|jsonld| ... } ⇒ Object, Hash

Frames the given input using the frame according to the steps in the Framing Algorithm. The input is used to build the framed output and is returned if there are no errors. If there are no matches for the frame, null must be returned. Exceptions must be thrown if there are errors.

The resulting ‘Array` is either returned, or yielded if a block is given.

Parameters:

  • input (String, #read, Hash, Array) —

    The JSON-LD object to copy and perform the framing on.

  • frame (String, #read, Hash, Array) —

    The frame to use when re-arranging the data.

  • options (Hash{Symbol => Object}) (defaults to: {}) —

    See options in #initialize Other options passed to expand

Options Hash (options):

  • :embed ('@last', '@always', '@never', '@link') — default: '@link' —

    a flag specifying that objects should be directly embedded in the output, instead of being referred to by their IRI.

  • :explicit (Boolean) — default: false —

    a flag specifying that for properties to be included in the output, they must be explicitly declared in the framing context.

  • :requireAll (Boolean) — default: true
  • :omitDefault (Boolean) — default: false —

    a flag specifying that properties that are missing from the JSON-LD input should be omitted from the output.

  • :expanded (Boolean) —

    Input is already expanded

Yields:

  • jsonld

Yield Parameters:

  • jsonld (Hash) —

    The framed JSON-LD document

Yield Returns:

  • (Object) —

    returned object

Returns:

  • (Object, Hash) —

    If a block is given, the result of evaluating the block is returned, otherwise, the framed JSON-LD document

Raises:

See Also:



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# File 'lib/json/ld/api.rb', line 315

def self.frame(input, frame, options = {})
  result = nil
  options = {
    base:           input.is_a?(String) ? input : '',
    compactArrays:  true,
    embed:          '@last',
    explicit:       false,
    requireAll:     true,
    omitDefault:    false,
    documentLoader: method(:documentLoader)
  }.merge!(options)

  framing_state = {
    graphs:       {'@default' => {}, '@merged' => {}},
    subjectStack: [],
    link:         {},
  }

  # de-reference frame to create the framing object
  frame = case frame
  when Hash then frame.dup
  when IO, StringIO then MultiJson.load(frame.read)
  when String
    remote_doc = options[:documentLoader].call(frame)
    case remote_doc.document
    when String then MultiJson.load(remote_doc.document)
    else remote_doc.document
    end
  end

  # Expand input to simplify processing
  expanded_input = options[:expanded] ? input : API.expand(input, options)

  # Expand frame to simplify processing
  expanded_frame = API.expand(frame, options)

  # Initialize input using frame as context
  API.new(expanded_input, nil, options) do
    #debug(".frame") {"context from frame: #{context.inspect}"}
    debug(".frame") {"expanded frame: #{expanded_frame.to_json(JSON_STATE) rescue 'malformed json'}"}

    # Get framing nodes from expanded input, replacing Blank Node identifiers as necessary
    old_dbg, @options[:debug] = @options[:debug], nil
    create_node_map(value, framing_state[:graphs], '@merged')
    @options[:debug] = old_dbg
    framing_state[:subjects] = framing_state[:graphs]['@merged']
    debug(".frame") {"subjects: #{framing_state[:subjects].to_json(JSON_STATE) rescue 'malformed json'}"}

    result = []
    frame(framing_state, framing_state[:subjects].keys.sort, (expanded_frame.first || {}), options.merge(parent: result))
    debug(".frame") {"after frame: #{result.to_json(JSON_STATE) rescue 'malformed json'}"}
    
    # Initalize context from frame
    @context = depth {@context.parse(frame['@context'])}
    # Compact result
    compacted = depth {compact(result, nil)}
    compacted = [compacted] unless compacted.is_a?(Array)

    # Add the given context to the output
    kwgraph = context.compact_iri('@graph', quiet: true)
    result = context.serialize.merge({kwgraph => compacted})
    debug(".frame") {"after compact: #{result.to_json(JSON_STATE) rescue 'malformed json'}"}
    result = cleanup_preserve(result)
  end

  block_given? ? yield(result) : result
end

.fromRdf(input, options = {}) {|jsonld| ... } ⇒ Object, Hash Also known as: fromRDF

Take an ordered list of RDF::Statements and turn them into a JSON-LD document.

The resulting ‘Array` is either returned or yielded, if a block is given.

Parameters:

  • input (Array<RDF::Statement>)
  • options (Hash{Symbol => Object}) (defaults to: {}) —

    See options in #initialize

Yields:

  • jsonld

Yield Parameters:

  • jsonld (Hash) —

    The JSON-LD document in expanded form

Yield Returns:

  • (Object) —

    returned object

Returns:

  • (Object, Hash) —

    If a block is given, the result of evaluating the block is returned, otherwise, the expanded JSON-LD document



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# File 'lib/json/ld/api.rb', line 473

def self.fromRdf(input, options = {}, &block)
  options = {useNativeTypes: false}.merge!(options)
  result = nil

  API.new(nil, nil, options) do |api|
    result = api.from_statements(input)
  end

  block_given? ? yield(result) : result
end

.toRdf(input, options = {}) {|statement| ... } ⇒ RDF::Enumerable Also known as: toRDF

Processes the input according to the RDF Conversion Algorithm, calling the provided callback for each triple generated.

Parameters:

  • input (String, #read, Hash, Array) —

    The JSON-LD object to process when outputting statements.

  • options ({Symbol,String => Object}) (defaults to: {}) —

    See options in #initialize Options passed to expand

Options Hash (options):

  • :produceGeneralizedRdf (Boolean) — default: false —

    If true, output will include statements having blank node predicates, otherwise they are dropped.

  • :expanded (Boolean) —

    Input is already expanded

Yields:

  • statement

Yield Parameters:

  • statement (RDF::Statement)

Returns:

  • (RDF::Enumerable) —

    set of statements, unless a block is given.

Raises:



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# File 'lib/json/ld/api.rb', line 398

def self.toRdf(input, options = {}, &block)
  unless block_given?
    results = []
    results.extend(RDF::Enumerable)
    self.toRdf(input, options) do |stmt|
      results << stmt
    end
    return results
  end

  # Expand input to simplify processing
  expanded_input = options[:expanded] ? input : API.expand(input, options.merge(ordered: false))

  API.new(expanded_input, nil, options) do
    # 1) Perform the Expansion Algorithm on the JSON-LD input.
    #    This removes any existing context to allow the given context to be cleanly applied.
    debug(".toRdf") {"expanded input: #{expanded_input.to_json(JSON_STATE) rescue 'malformed json'}"}

    # Generate _nodeMap_
    graphs = {'@default' => {}}
    create_node_map(expanded_input, graphs)
    debug(".toRdf") {"node map: #{graphs.to_json(JSON_STATE) rescue 'malformed json'}"}

    # Start generating statements
    graphs.each do |graph_name, graph|
      context = as_resource(graph_name) unless graph_name == '@default'
      debug(".toRdf") {"context: #{context ? context.to_ntriples : 'null'}"}
      # Drop results for graphs which are named with relative IRIs
      if graph_name.is_a?(RDF::URI) && !graph_name.absolute
        debug(".toRdf") {"drop relative graph_name: #{statement.to_ntriples}"}
        next
      end
      graph_to_rdf(graph) do |statement|
        next if statement.predicate.node? && !options[:produceGeneralizedRdf]
        # Drop results with relative IRIs
        relative = statement.to_a.any? do |r|
          case r
          when RDF::URI
            r.relative?
          when RDF::Literal
            r.has_datatype? && r.datatype.relative?
          else
            false
          end
        end
        if relative
          debug(".toRdf") {"drop statement with relative IRIs: #{statement.to_ntriples}"}
          next
        end

        statement.context = context if context
        if block_given?
          yield statement
        else
          results << statement
        end
      end
    end
  end
end