code: def _concatenate_base(space, items, out):
      return np.stack(items, axis=0, out=out)
  
file_path: gym/gym/vector/utils/numpy_utils.py
imports: from collections import OrderedDict
  from functools import singledispatch
  from typing import Iterable, Union
  import numpy
  from gym.spaces import Box, Dict, Discrete, MultiBinary, MultiDiscrete, Space, Tuple
label_desc: Use image node_id 2 for calling a global function with example usage: _concatenate_base(space, items, out) and returns: np