How to use the vine.barrier function in vine

producer=None, link=None, link_error=None, **options):
        args = args if args else ()
        if link is not None:
            raise TypeError('Cannot add link to group: use a chord')
        if link_error is not None:
            raise TypeError(
                'Cannot add link to group: do that on individual tasks')
        app = self.app
        if app.conf.task_always_eager:
            return self.apply(args, kwargs, **options)
        if not self.tasks:
            return self.freeze()

        options, group_id, root_id = self._freeze_gid(options)
        tasks = self._prepared(self.tasks, [], group_id, root_id, app)
        p = barrier()
        results = list(self._apply_tasks(tasks, producer, app, p,
                                         args=args, kwargs=kwargs, **options))
        result = self.app.GroupResult(group_id, results, ready_barrier=p)
        p.finalize()

        # - Special case of group(A.s() | group(B.s(), C.s()))
        # That is, group with single item that's a chain but the
        # last task in that chain is a group.
        #
        # We cannot actually support arbitrary GroupResults in chains,
        # but this special case we can.
        if len(result) == 1 and isinstance(result[0], GroupResult):
            result = result[0]

        parent_task = app.current_worker_task
        if add_to_parent and parent_task:

def __init__(self, results, app=None, ready_barrier=None, **kwargs):
        self._app = app
        self.results = results
        self.on_ready = promise(args=(self,))
        self._on_full = ready_barrier or barrier(results)
        if self._on_full:
            self._on_full.then(promise(self._on_ready, weak=True))