class ActiveModel::Serializer

def serializer_for(resource, options = {})
  if resource.respond_to?(:serializer_class)
    resource.serializer_class
  elsif resource.respond_to?(:to_ary)
    if Object.constants.include?(:ArraySerializer)
      ::ArraySerializer
    else
      ArraySerializer
    end
  else
    klass_name = build_serializer_class(resource, options)
    Serializer.serializers_cache.fetch_or_store(klass_name) do
      _const_get(klass_name)
    end
  end
end