Exercise 2: Submit, Leak, Submit More, Verify FIFO Order Throughout — Possible Solution
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THE SEQUENCE
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    lb = LeakyBucket(capacity=10)
    first_10 = [lb.add_request(f'req-{i}') for i in range(10)]   # fills the bucket exactly
    leaked_3 = [lb.leak() for _ in range(3)]                      # frees 3 slots
    next_8 = [lb.add_request(f'req-{i}') for i in range(10, 18)]  # only 3 slots free

RESULTS
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    first 10 submitted, all accepted: True | queue size: 10
    leaked 3: ['req-0', 'req-1', 'req-2'] | queue size now: 7
    next 8 submission results: [True, True, True, False, False, False, False, False]
    accepted: 3 | rejected: 5
    queue size after: 10 (capped at capacity)

VERIFYING THE CAPACITY LIMIT IS RESPECTED AT THE MOMENT OF SUBMISSION
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After leaking 3, the queue had exactly 3 free slots (7 used out of a
capacity of 10). Of the 8 newly-submitted requests, exactly the first
3 were accepted (filling the queue back to capacity 10), and the
remaining 5 were correctly rejected - add_request() checks
len(self.queue) >= self.capacity at the moment each individual request
arrives, not against some earlier snapshot.

VERIFYING FULL FIFO ORDER ACROSS BOTH SUBMISSION BATCHES
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    remaining leaked out, in order: ['req-3', 'req-4', 'req-5', 'req-6', 'req-7', 'req-8', 'req-9', 'req-10', 'req-11', 'req-12']
    full leak order: ['req-0', 'req-1', 'req-2', 'req-3', ..., 'req-12']
    matches expected FIFO order: True

Leaking out everything remaining produced req-3 through req-9 (the
rest of the FIRST batch, still queued in their original order) BEFORE
req-10 through req-12 (the accepted portion of the SECOND batch) -
exactly matching pure first-in-first-out order across the entire
sequence, even though the two batches were submitted at genuinely
different points with a leak() call in between.

WHY THIS WORKS AS AN ANSWER
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The sequence directly interleaves submission and leaking using this
chapter's own LeakyBucket unmodified, the capacity check is verified
firing correctly against the queue's actual current occupancy rather
than a stale count, and the full leak order is checked end to end
against the expected FIFO sequence rather than only spot-checked.