def get_common_xfix(series, xfix="suffix"):
    """
    Finds the longest common suffix or prefix of all the values in a series
    """
    common_xfix = ""
    while True:
        common_xfixes = (
            series.str[-(len(common_xfix) + 1) :]
            if xfix == "suffix"
            else series.str[: len(common_xfix) + 1]
        )  # first few or last few characters
        if (
            common_xfixes.nunique() != 1
        ):  # we found the character at which we don't have a unique xfix anymore
            break
        elif (
            common_xfix == common_xfixes.values[0]
        ):  # the entire first row is a prefix of every other row
            break
        else:  # the first or last few characters are still common across all rows - let's try to add one more
            common_xfix = common_xfixes.values[0]
    return common_xfix

    Finds the longest common suffix or prefix of all the values in a series
    
lib/openai/validators.py