code: def discard(self, *args):
          '''
          cplan.discard(...) yields a new calculation plan identical to cplan except without any of
          the calculation steps listed in the arguments.
          '''
          return Plan(reduce(lambda m,k: m.discard(k), args, self.nodes)f discard(self, *args):
          '''
          cplan.discard(...) yields a new calculation plan identical to cplan except without any of
          the calculation steps listed in the arguments.
          '''
          return Plan(reduce(lambda m,k: m.discard(k), args, self.nodes))
docs: cplan.discard(...) yields a new calculation plan identical to cplan except without any of
          the calculation steps listed in the arguments.