Для меня ясно, что я создаю список со списками внутри с кортежами внутри.Но как я проверяю правильную позицию королевы?Спасибо всем

Question

BOARD_SIZE = 4

def under_attack(col, queens): #does the 2nd argument takes all possible solution from smaller_solution or it takes one by one? 
    left = right = col

    for c, r in reversed (queens):
        left, right = left - 1, right + 1

        if r in (left, col, right):
            return True
    return False

def solve(n):
    if n == 0:
        return [[]]

    smaller_solutions = solve(n - 1)

    return [solution+[(n,i+1)]
        for i in range(BOARD_SIZE)
        for solution in smaller_solutions
        if not under_attack(i+1, solution]
for answer in solve(BOARD_SIZE):
    print (answer)