text: """
  Test module.
  """
  import itertools
  
  
  def powerset(iterable, maxSets=None):
      """
      powerset([1,2,3]) --> () (1,) (2,) (3,) (1,2) (1,3) (2,3) (1,2,3)
  
      See https://docs.python.org/2/library/itertools.html#recipes
      """
      s = list(iterable)
      return itertools.islice(itertools.chain.from_iterable(
          itertools.combinations(s, r) for r in range(len(s) + 1)),
          0, maxSets)
  