public Builder addField(
          com.google.protobuf.DescriptorProtos.FieldDescriptorProto.Builder builderForValue) {
        if (fieldBuilder_ == null) {
          ensureFieldIsMutable();
          field_.add(builderForValue.build());
          onChanged();
        } else {
          fieldBuilder_.addMessage(builderForValue.build());
        }
        return this;
      }