class ActiveModelSerializers::Adapter::JsonApi::ResourceIdentifier

def as_json
  { id: id, type: type }
end

def id_for(serializer)
  serializer.read_attribute_for_serialization(:id).to_s
end

def initialize(serializer, options)
  @id   = id_for(serializer)
  @type = JsonApi.send(:transform_key_casing!, type_for(serializer),
    options)
end

def type_for(serializer)
  return serializer._type if serializer._type
  if ActiveModelSerializers.config.jsonapi_resource_type == :singular
    serializer.object.class.model_name.singular
  else
    serializer.object.class.model_name.plural
  end
end