threading.Queue — Producer / Consumer

Implement solve(items, num_consumers) using the producer/consumer pattern:

1. A producer thread puts each item from items into a queue.Queue.
2. num_consumers consumer threads each pop items, double the value, and store results.
3. Return the results sorted ascending (order is non-deterministic with threads).

Examples

• solve([1, 2, 3], 2) → [2, 4, 6]
• solve([5], 1) → [10]

Constraints

• Use queue.Queue for thread-safe communication.
• Signal consumers with sentinel values (None) when production is done.
• All threads must finish before returning.