2739         self._gen = gen

  2739         self._gen = gen

  2740         self._cache = {}

  2740         self._cache = {}

  2741         self._genlist = baseset([])

  2741         self._genlist = baseset([])

  2742         self._finished = False

  2742         self._finished = False

  2743 

  2743 

  2744     def __contains__(self, x):

  2749     def __contains__(self, x):

  2745         if x in self._cache:

  2750         if x in self._cache:

  2746             return self._cache[x]

  2751             return self._cache[x]

  2747 

  2752 

  2748         # Use new values only, as existing values would be cached.

  2753         # Use new values only, as existing values would be cached.