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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 async def grant(self, acl='login'):
 """Set access level of this user on the controller. :param str acl: Access control ('login', 'add-model', or 'superuser') """

        if await self.controller.grant(self.username, acl):
            self._user_info.access = acl