def METHOD_NAME(self, func):
    # type: (Callable[[Optional[Union[Span, Context]]], Any]) -> Callable[[Optional[Union[Span, Context]]], Any]
    """Unregister a function registered to execute when a span is activated.
    Can be used as a decorator.
    :param func: The function to stop calling when a span is activated.
    """
    self._hooks.deregister(self.activate, func)
    return func