def mix_items(items_1, items_2, items_1_chunk_size=5, items_2_chunk_size=1):
    result_set = set()
    #
    items_1_iter = filterfalse(result_set.__contains__, items_1)
    items_2_iter = filterfalse(result_set.__contains__, items_2)
    #
    for iterator, chunk_size in cycle([
        (items_1_iter, items_1_chunk_size),
        (items_2_iter, items_2_chunk_size)
    ]):
        chunk = list(islice(iterator, chunk_size))
        if chunk:
            result_set.update(chunk)
            yield from chunk
        else:
            break
    #
    yield from items_1_iter
    yield from items_2_iter