code: def _split_generators(self, dl_manager):
      
      path = dl_manager.manual_dir
      train_path = os.path.join(path, _TRAIN_DIR)
      val_path = os.path.join(path, _VALIDATION_DIR)
  
      if not tf.io.gfile.exists(train_path) or not tf.io.gfile.exists(val_path):
        msg = ("You must download the dataset folder from CheXpert"
               "website manually and place it into %s." % path)
        raise AssertionError(msg)
  
      return [
          tfds.core.SplitGenerator(
              name=tfds.Split.TRAIN,
              num_shards=100,
              gen_kwargs={
                  "imgs_path": path,  # Relative img path is provided in csv
                  "csv_path": os.path.join(path, _TRAIN_LABELS_FNAME)
              },
          ),
          tfds.core.SplitGenerator(
              name=tfds.Split.VALIDATION,
              num_shards=10,
              gen_kwargs={
                  "imgs_path": path,
                  "csv_path": os.path.join(path, _VALIDATION_LABELS_FNAME)
              },
          ),
      ]
docs: Returns SplitGenerators.