Method HasNext

common/values/value_builder.cc:885–885

      : begin_(map->begin()), end_(map->end()) {}

  bool HasNext() override { return begin_ != end_; }

  absl::Status Next(const google::protobuf::DescriptorPool* absl_nonnull descriptor_pool,
                    google::protobuf::MessageFactory* absl_nonnull message_factory,