@commit_when_no_transaction
    def push_back(self, value):
        self.cache.push_back(self.value_pickler.dumps(value))
        return self
Given a forum, checks whether the user can append topics to it.
dataset/ETHPy150Open lsbardel/python-stdnet/stdnet/odm/struct.py/Sequence.push_back--crossover with--dataset/ETHPy150Open ellmetha/django-machina/machina/apps/forum_permission/handler.py/PermissionHandler.can_add_topic