# File lib/mongo_mapper/plugins/keys.rb, line 301
      def to_mongo(include_abbreviatons = true)
        BSON::OrderedHash.new.tap do |attrs|
          self.class.unaliased_keys.each do |name, key|
            value = self.read_key(key.name)
            if key.type == ObjectId || !value.nil?
              attrs[include_abbreviatons && key.persisted_name || name] = key.set(value)
            end
          end

          embedded_associations.each do |association|
            if documents = instance_variable_get(association.ivar)
              if association.is_a?(Associations::OneAssociation)
                attrs[association.name] = documents.to_mongo
              else
                attrs[association.name] = documents.map(&:to_mongo)
              end
            end
          end
        end
      end