code: def __call__(self, item):
      return np.stack([obj(item) for obj in self.objects])
  
imports: import re
  from dataclasses import dataclass, InitVar, field
  from itertools import chain
  from typing import Any, Dict, List, Union, Optional, ClassVar
  import numpy
  from toolz import valfilter, valmap
label_desc: Use image node_id 1 for calling the Stack obj's underlying member method code with example usage: obj.__call__(item) and returns: np