class_docstr: DQN that allows maxQ also backpropagate gradients.
code: def saved_attributes(self):
      # ResidualDQN doesn't use target models
      return ("model", "optimizer")
  
file_path: chainerrl/chainerrl/agents/residual_dqn.py
imports: from chainerrl.agents.dqn import DQN
  from chainerrl.functions import scale_grad
label_desc: Use image node_id 5 for calling the ResidualDQN obj's underlying member method code with example usage: obj.saved_attributes() and returns: str,  str