code: def expand(self, vs=None, conj=False):
          
          vs = self._expect_vars(vs)
          if vs:
              outer, inner = (And, Or) if conj else (Or, And)
              terms = [inner(self.restrict(p),
                             *boolfunc.point2term(p, conj))
                       for p in boolfunc.iter_points(vs)]
              if conj:
                  terms = [term for term in terms if term is not One]
              else:
                  terms = [term for term in terms if term is not Zero]
              return outer(*terms, simplify=False)
          else:
              return self
docs: Return the Shannon expansion with respect to a list of variables.