message: Support backend configuration strings
diff: @@ -34,13 +34,10 @@ unordered_set<string> BackendManager::ng_supported_backends_(
  ng_supported_backends.begin(), ng_supported_backends.end());
  Status BackendManager::SetBackendName(const string& backend_name) {
  - // Should check if the backend is supported only {"INTERPRETER","CPU"}
  - // currently Should also check if the backend library exists????
  std::lock_guard<std::mutex> lock(BackendManager::ng_backend_name_mutex_);
  - auto itr = BackendManager::ng_supported_backends_.find(backend_name);
  - if (itr == BackendManager::ng_supported_backends_.end()) {
  + if (backend_name.empty() || !IsSupportedBackend(backend_name)) {
  return errors::Internal("Backend ", backend_name,
  - " is not suported on nGraph");
  + " is not supported on nGraph");
  }
  BackendManager::ng_backend_name_ = backend_name;
  return Status::OK();
  @@ -80,7 +77,8 @@ unordered_set<string> BackendManager::GetSupportedBackendNames() {
  }
  bool BackendManager::IsSupportedBackend(const string& backend_name) {
  - auto itr = BackendManager::ng_supported_backends_.find(backend_name);
  + auto itr = BackendManager::ng_supported_backends_.find(
  + backend_name.substr(0, backend_name.find(':')));
  if (itr == BackendManager::ng_supported_backends_.end()) {
  return false;
  }
  