code: def check(self, inst, value):
          
          if not (self.or_none and value is None):
              if self.seq:
                  self.checktype_seq(value, self.kind,
                                     unique=self.unique, inst=inst)
              else:
                  self.checktype(value, self.kind, inst=inst)
docs: Raise TypeError if value doesn't satisfy the constraints
          for use on instance inst.