docstr: update the target network with the training network
  
  Args:
      decay(float): the decaying factor while updating the target network with the training network.
                  0 represents the **assignment**. None represents updating the target network slowly that depends on the hyperparameter `tau`.
docstr_tok: ["update","the","target","network","with","the","training","network","Args",":","decay","(","float",")",":","the","decaying","factor","while","updating","the","target","network","with","the","training","network",".","0","represents","the","*","*","assignment","*","*",".","None","represents","updating","the","target","network","slowly","that","depends","on","the","hyperparameter","`","tau","`","."]
code: def sync_target(self, decay=None):
      """update the target network with the training network
  
      Args:
          decay(float): the decaying factor while updating the target network with the training network.
                      0 represents the **assignment**. None represents updating the target network slowly that depends on the hyperparameter `tau`.
      """
      if decay is None:
          decay = 1.0 - self.tau
      self.model.sync_weights_to(self.target_model, decay=decay)
  
file_path: PARL/parl/algorithms/paddle/ddpg.py
imports: import parl
  import paddle
  import paddle.nn.functional
  from copy import deepcopy
  from parl.utils.utils import check_model_method
label_desc: Use image node_id 6 for calling the DDPG obj's underlying member method code with example usage: obj.sync_target(decay) without return types