const char* device = TFE_TensorHandleDeviceName(input, status);
  if (TF_GetCode(status) != TF_OK) return nullptr;
  TFE_OpSetDevice(op.get(), device, status);
  if (TF_GetCode(status) != TF_OK) return nullptr;
  TFE_OpSetAttrType(op.get(), "T", TFE_TensorHandleDataType(input));
  TFE_OpSetAttrInt(op.get(), "group_size", group_size);
  TFE_OpSetAttrInt(op.get(), "group_key", 0);
  TFE_OpSetAttrInt(op.get(), "instance_key", 0);