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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 set_compression_pool_size(pool_size):
 """ Set the size of the compression workers thread pool. If the pool is already created, it waits until all jobs are finished, and then proceeds with setting the new size. Parameters pool_size : `int` The size of the pool (must be a positive integer) Returns ------- `None` """

    pool_size = int(pool_size)
    if pool_size < 1:
        raise ValueError("The compression thread pool size cannot be of size {}".format(pool_size))

    global _compress_thread_pool
    if _compress_thread_pool is not None:
        _compress_thread_pool.close()
        _compress_thread_pool.join()
    _compress_thread_pool = ThreadPool(pool_size)