add_cached_associations

# File activerecord/lib/active_record/message_pack.rb, line 81
      def add_cached_associations(record, entry)
        record.class.normalized_reflections.each_value do |reflection|
          if record.association_cached?(reflection.name) && record.association(reflection.name).loaded?
            entry << reflection.name << encode(record.association(reflection.name).target)
          end
        end
      end