code: def pred_batch(self, obs, stage_idx):
      batch_obs = np.expand_dims(obs, axis=0).astype("float32")
      if stage_idx == 0:
          action = self.start_model.pred_batch(batch_obs)
      else:
          action = self.stage123_model.pred_batch(batch_obs)
      return action
  
imports: import numpy
  import parl.layers
  from mlp_model import ActorModel, CriticModel
  from paddle import fluid
  from parl.utils import logger
label_desc: Use image node_id 2 for calling the SubmitModel obj's underlying member method code with example usage: obj.pred_batch(obs, stage_idx) and returns: action