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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:
 def wait(fs, timeout=None, return_when=ALL_COMPLETED):
 """Wait for the futures in the given sequence to complete. Args: fs: The sequence of Futures (possibly created by different Executors) to wait upon. timeout: The maximum number of seconds to wait. If None, then there is no limit on the wait time. return_when: Indicates when this function should return. The options are: FIRST_COMPLETED - Return when any future finishes or is cancelled. FIRST_EXCEPTION - Return when any future finishes by raising an exception. If no future raises an exception then it is equivalent to ALL_COMPLETED. ALL_COMPLETED - Return when all futures finish or are cancelled. Returns: A named 2-tuple of sets. The first set, named 'done', contains the futures that completed (is finished or cancelled) before the wait completed. The second set, named 'not_done', contains uncompleted futures. """

    with _AcquireFutures(fs):
        done = set(f for f in fs
                   if f._state in [CANCELLED_AND_NOTIFIED, FINISHED])
        not_done = set(fs) - done

        if (return_when == FIRST_COMPLETED) and done:
            return DoneAndNotDoneFutures(done, not_done)
        elif (return_when == FIRST_EXCEPTION) and done:
            if any(f for f in done
                   if not f.cancelled() and f.exception() is not None):
                return DoneAndNotDoneFutures(done, not_done)

        if len(done) == len(fs):
            return DoneAndNotDoneFutures(done, not_done)

        waiter = _create_and_install_waiters(fs, return_when)

    waiter.event.wait(timeout)
    for f in fs:
        with f._condition:
            f._waiters.remove(waiter)

    done.update(waiter.finished_futures)
    return DoneAndNotDoneFutures(done, set(fs) - done)