'Callable version for use as a decorator
:param func: Function to call initially and every time the
children change. `func` will be called with a
single argument, the list of children.
:type func: callable'

def __call__(self, func):

    if self._used:
        raise KazooException('A    function    has    already    been    associated    with    this    ChildrenWatch    instance.')
    self._func = func
    self._used = True
    if self._allow_session_lost:
        self._client.add_listener(self._session_watcher)
    self._get_children()
    return func
