Generic method to setLevel for handlers.

def _set_min_level(self, handler_class, level):
        """Generic method to setLevel for handlers."""
        if self._exist_handler(handler_class):
            if not level:
                self._delete_handler(handler_class)
            else:
                self._update_handler(handler_class, level=level)
        elif level:
            self._create_handler(handler_class, level)