def _is_visible(idx_row, idx_col, lengths):
    '\n    Index -> {(idx_row, idx_col): bool}).\n    '
    return ((idx_col, idx_row) in lengths)
Index -> {(idx_row, idx_col): bool}).
def _is_visible(idx_row, idx_col, lengths):
    '\n    \n    '
    return ((idx_col, idx_row) in lengths)