code: def _condense(self, data):
      '''
      Condense by or-ing all of the sets.
      '''
      if data:
        return reduce(operator.ior, data.values())
      return set(f _condense(self, data):
      '''
      Condense by or-ing all of the sets.
      '''
      if data:
        return reduce(operator.ior, data.values())
      return set()
docs: Condense by or-ing all of the sets.