Disable the restricted buttons

        :returns: None
        :rtype: None
        :raises: None

def disable_restricted(self, ):
        """Disable the restricted buttons

        :returns: None
        :rtype: None
        :raises: None
        """
        todisable = [(self.reftrack.duplicate, self.duplicate_tb),
                     (self.reftrack.delete, self.delete_tb),
                     (self.reftrack.reference, self.reference_tb),
                     (self.reftrack.replace, self.replace_tb),]
        for action, btn in todisable:
            res = self.reftrack.is_restricted(action)
            btn.setDisabled(res)