<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def set_number(self, key, value):
 """ set a key's value """

        storage = self.storage

        if not isinstance(value, int):
            logger.error("set_number: Value must be an integer")
            return

        try:
            lock.acquire()
            storage[key] = value
        finally:
            self.storage._p_changed = True
            lock.release()

        return storage[key]