code: def validate(self, answer):
          
          if answer is None:
              return False
          else:
              if isinstance(self.validator, list):
                  for v in self.validator:
                      if not v.validate(answer):
                          return False
                  return True
              else:
                  return self.validator.validate(answer)
docs: Validate the answer with our Validator(s)
  
              This will support one or more validator classes being applied to
              this question.  If there are multiple, all validators must return
              True for the answer to be valid.