python

    def __delattr__(self, name):
        """ Remove non-slot field attribute. """
        try:
            del self._attrs[name]
        except KeyError:
            raise AttributeError(name)

    def __str__(self):
        return "%s.%s" % (self.model_name, self.name)

    def __repr__(self):
        return "%s.%s" % (self.model_name, self.name)