code: def validate_path_exists(s):
      """If s is a path, return s, else False"""
      if s is None:
          return None
      if os.path.exists(s):
          return s
      else:
          raise RuntimeError(
              '"%s" should be a path but it does not exist' % s
          )
  
imports: from __future__ import absolute_import, division, print_function
  import six
  from functools import reduce
  import operator
  import os
  import warnings
  import re
  from matplotlib import cbook, testing
  from matplotlib.cbook import mplDeprecation, deprecated, ls_mapper
  from matplotlib.fontconfig_pattern import parse_fontconfig_pattern
  from matplotlib.colors import is_color_like
  from cycler import Cycler, cycler
label_desc: Use image node_id 3 for calling a global function with example usage: validate_path_exists(s) and returns: None, s