def METHOD_NAME(self):
    """Validate the current value of the widget.
    If a problem is found, the widget will be put into an error state.
    """
    for validator in self.validators:
        error_message = validator(self.value)
        if error_message is not None:
            self._impl.set_error(error_message)
            break
    else:
        self._impl.clear_error()