def METHOD_NAME(masks_num):
    masks_producers = []
    for j in range(0, masks_num * 2, 2):
        masks_producers.append([SymbolicMaskProducer(i, i + 1) for i in range(j, j + 2)])
    masks = [SymbolicMask(i, producers) for i, producers in enumerate(masks_producers)]
    concated_mask = SymbolicMaskProcessor.concatenate(masks, axis=0)
    assert concated_mask.shape[0] == sum([mask.shape[0] for mask in masks])
    assert len(concated_mask.mask_producers) == len(masks) * 2
    for idx, mask_producer in enumerate(concated_mask.mask_producers):
        cur_mask_producer = masks_producers[idx // 2][idx % 2]
        assert cur_mask_producer is mask_producer