Fix Thread-Safe Trigger Synchronization

You are implementing a thread-safe trigger in Python. The trigger has an internal boolean flag, initially `False`. Requirements: - `wait()` blocks until the trigger has fired. - `fire()` sets the flag to `True` and wakes all waiting threads. - If `fire()` is called before `wait()`, future calls to `wait()` should return immediately. - Multiple threads may call `wait()` and `fire()` concurrently. Consider the following follow-up code fragment inside `fire()`: ```python self.lock.acquire() self.lock.release() self.flag = True ``` Is this thread-safe? Explain what can go wrong and show a correct implementation approach.