public Builder mergeFrom(org.box2d.proto.Box2D.PbFixture other) {
        if (other == org.box2d.proto.Box2D.PbFixture.getDefaultInstance()) return this;
        if (other.hasTag()) {
          setTag(other.getTag());
        }
        if (other.hasRestitution()) {
          setRestitution(other.getRestitution());
        }
        if (other.hasFriction()) {
          setFriction(other.getFriction());
        }
        if (other.hasDensity()) {
          setDensity(other.getDensity());
        }
        if (other.hasSensor()) {
          setSensor(other.getSensor());
        }
        if (other.hasFilter()) {
          mergeFilter(other.getFilter());
        }
        if (other.hasShape()) {
          mergeShape(other.getShape());
        }
        this.mergeUnknownFields(other.getUnknownFields());
        return this;
      }