class ActiveModel::Serializer

def associate(klass, attrs) #:nodoc:
  options = attrs.extract_options!
  self._associations = _associations.dup
  attrs.each do |attr|
    unless method_defined?(attr)
      define_method attr do
        object.send attr
      end
    end
    define_include_method attr
    self._associations[attr] = klass.refine(attr, options)
  end
end