code: def _actor_learn(self, obs):
      actor_loss = -self.model.Q1(obs, self.model.policy(obs)).mean()
  
      self.actor_optimizer.clear_grad()
      actor_loss.backward()
      self.actor_optimizer.step()
  
      self.sync_target()
      return actor_loss
  
file_path: PARL/parl/algorithms/paddle/td3.py
imports: import parl
  import paddle
  import paddle.nn.functional
  from parl.utils.utils import check_model_method
  from copy import deepcopy
label_desc: Use image node_id 5 for calling the TD3 obj's underlying member method code with example usage: obj._actor_learn(obs) and returns: actor_loss