def idx_to_a1(row, col):
    """Convert a row & column to A1 notation. Adapted from gspread.utils.

    :param row: row index
    :param col: column index
    :return: A1 notation of row:column
    """
    div = col
    column_label = ""
    while div:
        (div, mod) = divmod(div, 26)
        if mod == 0:
            mod = 26
            div -= 1
        column_label = chr(mod + 64) + column_label
    return f"{column_label}{row}"