code: def _stack_arrs(arrs):
      if isinstance(arrs, list):
          # stack arrs if arrs is a list.
          return np.stack(arrs)
      else:
          # do nothing if arrs are not a list.
          return arrs
  
imports: from contextlib import closing
  import socket
  import sys
  import tempfile
  import shutil
  from bigdl.dllib.utils import log4Error
  from bigdl.dllib.utils.common import callBigDlFunc
  from bigdl.dllib.utils.file_utils import get_file_list, is_local_path
  from bigdl.orca.data import SparkXShards
  from bigdl.orca.data.utils import get_size
  from bigdl.orca.data.file import put_local_dir_tree_to_remote, put_local_file_to_remote, get_remote_file_to_local, get_remote_dir_to_local
  from bigdl.dllib.utils.utils import convert_row_to_numpy
  from functools import partial
  import numpy
  from bigdl.orca.common import SafePickle
  import os
  import subprocess
  from bigdl.dllib.utils.log4Error import *
label_desc: Use image node_id 9 for calling a global function with example usage: _stack_arrs(arrs) and returns: np, arrs