# File lib/orm_adapter/adapters/mongo_mapper.rb, line 54
      def conditions_to_fields(conditions)
        conditions.inject({}) do |fields, (key, value)|
          if value.is_a?(MongoMapper::Document) && klass.key?("#{key}_id")
            fields.merge("#{key}_id" => value.id)
          else
            fields.merge(key => value)
          end
        end
      end