docs: def listify(val, return_type=tuple):
      """
      Examples:
          >>> listify('abc', return_type=list)
          ['abc']
          >>> listify(None)
          ()
          >>> listify(False)
          (False,)
          >>> listify(('a', 'b', 'c'), return_type=list)
          ['a', 'b', 'c']
      """
      # TODO: flatlistify((1, 2, 3), 4, (5, 6, 7))
      if val is None:
          return return_type()
      elif isiterable(val):
          return return_type(val)
      else:
          return return_type((val, ))