code: def validate(self,
                   controls: Iterable[Tuple[str, str]],
                   subcontrol: str = None) -> Any:
          
          try:
              return super().validate(controls, subcontrol)
          except ValidationFailure as e:
              if DEBUG_FORM_VALIDATION:
                  log.warning("Validation failure: {!r}; {}",
                              e, self._get_form_errors())
              self._show_hidden_widgets_for_fields_with_errors(self)
              raise
docs: Validates the form.
  
          Args:
              controls: an iterable of ``(key, value)`` tuples
              subcontrol:
  
          Returns:
              a Colander ``appstruct``
  
          Raises:
              ValidationFailure: on failure