docstr: use actor model of self.models[model_id] to predict the action
          
docstr_tok: ["use","actor","model","of","self.models","[","model_id","]","to","predict","the","action"]
code: def predict(self, obs, model_id):
      """use actor model of self.models[model_id] to predict the action"""
      return self.models[model_id].policy(obs)
  
file_path: PARL/examples/NeurIPS2018-AI-for-Prosthetics-Challenge/multi_head_ddpg.py
imports: import parl
  from parl import layers
  from copy import deepcopy
  from paddle import fluid
label_desc: Use image node_id 2 for calling the MultiHeadDDPG obj's underlying member method code with example usage: obj.predict(obs, model_id) and returns: self