docstr: 使用self.model的网络来获取 [Q(s,a1),Q(s,a2),...]
          
code: def predict(self, obs):
      """使用self.model的网络来获取 [Q(s,a1),Q(s,a2),...]"""
      return self.model(obs)
  
file_path: PARL/examples/tutorials/parl2_dygraph/lesson3/dqn/algorithm.py
imports: import copy
  import parl
  import paddle
label_desc: Use image node_id 2 for calling the DQN obj's underlying member method code with example usage: obj.predict(obs) and returns: self