code: def recover(self, state):
          "recompute the actual value, then compare it against the truth"
          newval = self.f.recover(state)
          return self.errtype(self.value, newvalf recover(self, state):
          "recompute the actual value, then compare it against the truth"
          newval = self.f.recover(state)
          return self.errtype(self.value, newval)
docs: recompute the actual value, then compare it against the truth