code: def validate(self) -> None:
      if self.num_gpus > 1:
          raise ValueError(
              "`num_gpus` > 1 not yet supported for APEX-DQN!"
          )
      # Call DQN's validation method.
      super().validate()
  
file_path: ray/rllib/algorithms/apex_dqn/apex_dqn.py
imports: from typing import Optional
  from ray._private.dict import merge_dicts
  from ray.rllib.algorithms.algorithm_config import NotProvided
  from ray.rllib.algorithms.dqn.dqn import DQN, DQNConfig
  from ray.rllib.utils.annotations import override
  from ray.rllib.utils.deprecation import DEPRECATED_VALUE, Deprecated, ALGO_DEPRECATION_WARNING
label_desc: Use image node_id 3 for calling the ApexDQNConfig obj's underlying member method code with example usage: obj.validate() without return types