def get_max_pgs_index(df_ghat):
    """
    Purpose: to identify the column that holds the max polygenic score for each row

    Arguments:
        df_ghat: dataframe of polygenic scores, where each row is a new parent pair. 

    Returns:
        series of indices of the highest polygenic score per parent pair
    """
    return df_ghat.idxmax(axis=1).map(lambda x: int(x.lstrip('ghat_')))