code: def list_strings(arg):
      """Always return a list of strings, given a string or list of strings
      as input.
  
      Examples
      --------
      ::
  
          In [7]: list_strings('A single string')
          Out[7]: ['A single string']
  
          In [8]: list_strings(['A single string in a list'])
          Out[8]: ['A single string in a list']
  
          In [9]: list_strings(['A','list','of','strings'])
          Out[9]: ['A', 'list', 'of', 'strings']
      """
  
      if isinstance(arg, py3compat.string_types):
          return [arg]
      else:
          return arg
  
imports: from __future__ import absolute_import
  import os
  import re
  import sys
  import textwrap
  from string import Formatter
  from IPython.testing.skipdoctest import skip_doctest_py3, skip_doctest
  from IPython.utils import py3compat
label_desc: Use image node_id 2 for calling a global function with example usage: list_strings(arg) and returns: list, arg