public Builder mergeFilter(org.box2d.proto.Box2D.PbFilter value) {
        if (filterBuilder_ == null) {
          if (((bitField0_ & 0x00000020) == 0x00000020) &&
              filter_ != org.box2d.proto.Box2D.PbFilter.getDefaultInstance()) {
            filter_ =
              org.box2d.proto.Box2D.PbFilter.newBuilder(filter_).mergeFrom(value).buildPartial();
          } else {
            filter_ = value;
          }
          onChanged();
        } else {
          filterBuilder_.mergeFrom(value);
        }
        bitField0_ |= 0x00000020;
        return this;
      }