How to use the eventkit.ops.combine.AddableJoinOp function in eventkit

s = self._sources.popleft()
            cb = self._source2cb.pop(s, None)
            if cb:
                s.disconnect(cb, done=self.on_source_done)
        self.emit(*args)

    def on_source_done(self, source):
        cb = self._source2cb.pop(source)
        source.disconnect(cb, done=self.on_source_done)
        while source in self._sources:
            self._sources.remove(source)
        if not self._sources and self._parent is None:
            self.set_done()


class Chain(AddableJoinOp):
    __slots__ = ('_qq', '_source2cbs')

    def __init__(self, *sources):
        AddableJoinOp.__init__(self)
        self._qq = deque()
        self._source2cbs = defaultdict(list)  # map from source to callbacks
        self._set_sources(*sources)

    def add_source(self, source):
        if not self._sources:
            self._connect_from(source)
        else:
            def cb(*args):
                q.append(args)
            q = deque()
            self._qq.append(q)

source -= cb

    def on_source_s(self, source, *args):
        if source is not self._active_source:
            self._remove_source(self._active_source)
            self._active_source = source
        self.emit(*args)

    def on_source_done(self, source):
        self._remove_source(source)
        if not self._sources and self._parent is None:
            self._active_source = None
            self.set_done()


class Concat(AddableJoinOp):
    __slots__ = ('_source2cb',)

    def __init__(self, *sources):
        AddableJoinOp.__init__(self)
        self._source2cb = {}  # map from source to callback
        self._set_sources(*sources)

    def add_source(self, source):
        if source in self._sources:
            return
        self._sources.append(source)
        cb = self._source2cb.get(source)
        if not cb:
            cb = functools.partial(self._on_source_s, source)
            self._source2cb[source] = cb
            source.connect(cb, done=self.on_source_done)

parent.done_event += self._on_parent_done

    def on_source_done(self, source):
        self._disconnect_from(source)
        self._sources.remove(source)
        if not self._sources and self._parent is None:
            self.set_done()

    def _on_parent_done(self, parent):
        parent -= self._on_parent_done
        self._parent = None
        if not self._sources:
            self.set_done()


class Merge(AddableJoinOp):
    __slots__ = ()

    def add_source(self, source):
        self._sources.append(source)
        self._connect_from(source)


class Switch(AddableJoinOp):
    __slots__ = ('_source2cb', '_active_source')

    def __init__(self, *sources):
        AddableJoinOp.__init__(self)
        self._source2cb = {}  # map from source to callback
        self._active_source = None
        self._set_sources(*sources)

def _on_parent_done(self, parent):
        parent -= self._on_parent_done
        self._parent = None
        if not self._sources:
            self.set_done()


class Merge(AddableJoinOp):
    __slots__ = ()

    def add_source(self, source):
        self._sources.append(source)
        self._connect_from(source)


class Switch(AddableJoinOp):
    __slots__ = ('_source2cb', '_active_source')

    def __init__(self, *sources):
        AddableJoinOp.__init__(self)
        self._source2cb = {}  # map from source to callback
        self._active_source = None
        self._set_sources(*sources)

    def add_source(self, source):
        self._sources.append(source)
        cb = self._source2cb.get(source)
        if not cb:
            cb = functools.partial(self.on_source_s, source)
            self._source2cb[source] = cb
            source.connect(cb, done=self.on_source_done)