'Add many activities
:param activities: a list of activities
:param batch_interface: the batch interface'

def add_many(self, activities, batch_interface=None, trim=True, *args, **kwargs):

    validate_list_of_strict(activities, (self.activity_class, FakeActivity))
    add_count = self.timeline_storage.add_many(self.key, activities, batch_interface=batch_interface, *args, **kwargs)
    if (trim and (random.random() <= self.trim_chance)):
        self.trim()
    self.on_update_feed(new=activities, deleted=[])
    return add_count
