if (LookupResource(cc_ctx, HandleFromInput(cc_ctx, input), maybe_resource)
            .ok()) {
      return (*maybe_resource)->mu();
    } else {
      cc_ctx->CtxFailureWithWarning(
          tensorflow::errors::Internal("Invalid variable reference."));
      return nullptr;
    }
  }
  return cc_ctx->input_ref_mutex(input);
}

  do {                                                      \
    ::tensorflow::Status _s(__VA_ARGS__);                   \
    if (!TF_PREDICT_TRUE(_s.ok())) {                        \
      (CTX)->CtxFailureWithWarning(__FILE__, __LINE__, _s); \
      return RET;                                           \
    }                                                       \
  } while (0)

namespace tensorflow {

namespace {