docstr: use self.model (Q function) to predict the action values
          
code: def predict(self, obs):
      """use self.model (Q function) to predict the action values"""
      return self.model(obs)
  
file_path: PARL/parl/algorithms/paddle/ddqn.py
imports: import copy
  import parl
  import paddle
  from parl.utils.utils import check_model_method
label_desc: Use image node_id 2 for calling the DDQN obj's underlying member method code with example usage: obj.predict(obs) and returns: self