code: def _create_list(value, allow_filename=False):
      
      if isinstance(value, list):
          return value
      elif isinstance(value, string_type):
          if allow_filename and os.path.isfile(value):
              with codecs.open(value, 'r', encoding="utf-8") as handle:
                  return handle.read().splitlines()
          return value.split(',')
      else:
          raise ValueError("Can't create list for input {}".format(value))
docs: Create a list from the input value.
  
      If the input is a list already, return it.
      If the input is a comma-separated string, split it.