def serialize_relations(attributes = {}, options = {})
      inclusions = options[:include]
      relation_names(inclusions).each do |name|
        association = relations[name.to_s]
        if association && relation = send(association.name)
          attributes[association.name.to_s] =
            relation.serializable_hash(relation_options(inclusions, options, name))
        end
      end
    end
def serialize_relations(attributes = {}, options = {})
      inclusions = options[:include]
      relation_names(inclusions).each do |name|
        association = relations[name.to_s]
        if association && relation = send(association.name)
          attributes[association.name.to_s] =
            relation.serializable_hash(relation_options(inclusions, options, name))
        end
      end
    end
For each of the provided include options, get the association needed and
 provide it in the hash.

 @example Serialize the included associations.
   document.serialize_relations({}, :include => :addresses)

 @param [ Hash ] attributes The attributes to serialize.
 @param [ Hash ] options The serialization options.

 @option options [ Symbol ] :include What associations to include
 @option options [ Symbol ] :only Limit the fields to only these.
 @option options [ Symbol ] :except Dont include these fields.

 @since 2.0.0.rc.6