def METHOD_NAME(contig_var_nts_df, min_nt_freq):
    var_nts_dict = {}
    for pos, contig_var_nts_df in contig_var_nts_df.set_index('pos').groupby('pos', sort=False):
        total_nts_df = contig_var_nts_df.sum(axis=0)
        total_nts_freq_series = total_nts_df / total_nts_df.sum()
        total_nts_series = total_nts_df[total_nts_freq_series > min_nt_freq]
        total_nts_series = total_nts_series.loc[~total_nts_series.index.isin([total_nts_series.idxmax()])]
        if len(total_nts_series) == 0:
            continue
        var_nts_dict[pos] = tuple(total_nts_series.index)
    return var_nts_dict