from typing import List


def largestColumnSum(L: List[List[int]]) -> int:
    """Return the largest sum of any column in the matrix."""
    cols = [sum(col) for col in zip(*L)]
    return max(cols)


def testLargestColumnSum():
    print("Testing largestColumnSum()...", end="")
    L = [[1, 2, 3], [4, 5, 6]]
    assert largestColumnSum(L) == 9  # sum([3, 6])

    L = [[3, 2, 1], [-5, -3, -6]]
    assert largestColumnSum(L) == -1  # sum([2, -3])

    L = [[1, 2, 3], [4, 5, 6], [7, -1, -2]]
    assert largestColumnSum(L) == 12  # sum([1, 4, 7])

    L = [[7, -1, -2]]
    assert largestColumnSum(L) == 7  # sum([7])
    print("Passed!")


def main():
    testLargestColumnSum()


main()