ASSERT_EQ(TF_OK, TF_GetCode(s_)) << TF_Message(s_);
  TF_GraphCopyFunction(host_graph_, func_, grad_func2, s_);
  EXPECT_EQ(TF_INVALID_ARGUMENT, TF_GetCode(s_));
  EXPECT_EQ(string("Cannot assign gradient function 'MyGrad2' to 'MyFunc' "
                   "because it already has gradient function 'MyGrad1'"),
            string(TF_Message(s_)));

  TF_DeleteFunction(grad_func1);

		// it heal during the regular scanner cycle.
		dst := []byte{}
		for _, ver := range xlMeta.versions {
			dst = slices.Grow(dst, 16)
			copy(dst[len(dst):], ver.header.VersionID[:])
		}
		res.Sign = dst
	}

	newDstBuf, err := xlMeta.AppendTo(metaDataPoolGet())
	defer metaDataPoolPut(newDstBuf)
	if err != nil {
		if legacyPreserved {
			s.deleteFile(dstVolumeDir, legacyDataPath, true, false)