want to add media sequences to iiif manifest

manifest_behavior.rb

# frozen_string_literal: true
require 'iiif_manifest'
# how do i override or extend classes I would like to in iiif_manifest? for example these two methods in manifest_builder should be added to or extend the class locally. I think the better design would be to have them in the gem, they should be their own builder class like sequence_builder, and autoloaded, and used in the optional case of pdfs or other sequenced media and the universal viewer.

module PDFManifestBuilder
  def add_media_sequences(access_path, manifest)
    json_manifest = JSON.parse(manifest.to_json)
    json_manifest["mediaSequences"] = [media_sequence(access_path)]
    json_manifest["@context"] = ["http://iiif.io/api/image/2/context.json","http://wellcomelibrary.org/ld/ixif/0/context.json"]
    json_manifest
  end

  def media_sequence(access_path)
    @elements ||=
      begin
        elements = {}
        elements["@id"] = access_path
        elements["format"] = "application/pdf"
        elements["@type"] = "foaf:Document"
        elements["label"] = "Test Label"
        elements["rendering"] = [{
          "@id": access_path,
          "format": "application/pdf",
          "label": "Test Label"
          }]
        elements["thumbnail"] = "http://test_path_to_thumbnail.jpg"
      end
    @mediaSequence ||=
      begin
        mediaSequence = {}
        mediaSequence["@type"] ||= "ixif:MediaSequence"
        mediaSequence["label"] ||= "Contents"
        mediaSequence["rendering"] = []
        mediaSequence["elements"] = [elements]
        mediaSequence
      end
    end
end

module ManifestBehavior
  def manifest
    id = presenter.solr_document[:file_set_ids_ssim].first
    # access_url = DerivativePath.access_path(id)
    access_url = "/test.pdf"
    headers['Access-Control-Allow-Origin'] = '*'
    respond_to do |format|
      format.json { render json:
        # PDFManifestBuilder
        # only in case of pdf (so need to get that from presenter), add_media_sequences

        # this returns instance of ManifestBuilder
        # manifest_builder.add_media_sequences(access_url)
         manifest_builder(access_url) }
    end
  end

  private

    def manifest_builder(access_url)
      builder = IIIFManifest::ManifestFactory.new(presenter)
      builder.extend PDFManifestBuilder
      manifest = builder.to_h
      builder.add_media_sequences(access_url, manifest)
    end
end