public Builder setNormals(
          int index, org.box2d.proto.Box2D.PbVec2.Builder builderForValue) {
        if (normalsBuilder_ == null) {
          ensureNormalsIsMutable();
          normals_.set(index, builderForValue.build());
          onChanged();
        } else {
          normalsBuilder_.setMessage(index, builderForValue.build());
        }
        return this;
      }