ptr = new const char*[strs.size()];
      for (size_t i = 0; i < strs.size(); ++i) {
        ptr[i] = strs[i].c_str();
      }
    }
    return ptr;
  }

  // An explicit `num_opers` is needed so that we can distinguish between the
  // case of no operations specified (-1) and the case of an empty set of
  // operations specified (0).
  void DefineT(int num_opers, const std::vector<TF_Operation*>& opers,