docstr: Synchronize weights of self.model.policy_model to self.old_policy_model
          
docstr_tok: ["Synchronize","weights","of","self.model.policy_model","to","self.old_policy_model"]
code: def sync_old_policy(self):
      """Synchronize weights of self.model.policy_model to self.old_policy_model"""
      self.model.policy_model.sync_weights_to(self.old_policy_model)
  
file_path: PARL/parl/algorithms/fluid/ppo.py
imports: import warnings
  import numpy
  from copy import deepcopy
  from paddle import fluid
  from parl.core.fluid import layers
  from parl.core.fluid.algorithm import Algorithm
label_desc: Use image node_id 9 for calling the PPO obj's underlying member method code with example usage: obj.sync_old_policy() without return types