def sum_neg_off_diags_naive(m):
    """Returns sum of negative off-diags in m.

    Naive, slow implementation -- don't use. Primarily here to check correctness
    of faster implementation.
    """
    sum = 0
    for row_i, row in enumerate(m):
        for col_i, item in enumerate(row):
            if (row_i != col_i) and (item < 0):
                sum += item
    return sum