code: def policy(self, obs):
      return self.actor_model(obs)
  
file_path: PARL/examples/tutorials/parl2_dygraph/lesson5/homework/ddpg_quadrotor/quadrotor_model.py
imports: import parl
  import paddle
  import paddle.nn
  import paddle.nn.functional
label_desc: Use image node_id 2 for calling the QuadrotorModel obj's underlying member method code with example usage: obj.policy(obs) and returns: self