code: def __call__(self, x):
      return self.model(x)
  
file_path: towhee/tests/unittests/trainer/test_weights.py
imports: import unittest
  import torch
  import torchvision
  from pathlib import Path
  from towhee.trainer.utils.trainer_utils import STATE_CHECKPOINT_NAME
  from towhee.trainer.training_config import TrainingConfig
  from towhee.operator import NNOperator
  from towhee.trainer.modelcard import ModelCard
label_desc: Use image node_id 2 for calling the MockOperator obj's underlying member method code with example usage: obj.__call__(x) and returns: self