code: def __getitem__(self, item):
      return {"x": self.x[item], "y": self.y[item]}
  
imports: import pytest
  from fastNLP.core.callbacks import callback
  from fastNLP.core.controllers.trainer import Trainer
  from fastNLP.core.controllers.trainer import Evaluator
  from fastNLP.core.metrics.accuracy import Accuracy
  from fastNLP.core.callbacks.progress_callback import RichCallback
  from fastNLP.core.dataloaders.jittor_dataloader.fdl import JittorDataLoader
  from fastNLP.envs.imports import _NEED_IMPORT_JITTOR
label_desc: Use image node_id 3 for calling the JittorRandomMaxDataset obj's underlying member method code with example usage: obj.__getitem__(item) and returns: dict