message: [tf.data] Add logging to the performance modeling framework.
diff: @@ -380,7 +380,12 @@ std::shared_ptr<Node> Model::AddNode(Node::Factory factory, const string& name,
  output_ = node;
  }
  if (output) {
  + VLOG(3) << "Adding " << node->name() << "(id:" << node->id()
  + << ") as input for " << output->name() << "(id:" << output->id()
  + << ")";
  output->add_input(node);
  + } else {
  + VLOG(3) << "Adding " << node->name() << "(id:" << node->id() << ")";
  }
  collect_resource_usage_ =
  collect_resource_usage_ || node->has_tunable_parameters();
  @@ -493,10 +498,13 @@ void Model::RecordStop(const string& name, bool start_output) {
  void Model::RemoveNode(const string& name) {
  mutex_lock l(mu_);
  auto node = gtl::FindOrNull(lookup_table_, name);
  - if (node && (*node)->output()) {
  + if (node) {
  + if ((*node)->output()) {
  (*node)->output()->remove_input(*node);
  }
  + VLOG(3) << "Removing " << (*node)->name() << "(id:" << (*node)->id() << ")";
  remove_node_hook_(*node);
  + }
  lookup_table_.erase(name);
  }
  