def slim_down_df(godb, df_clean, go_colname):
    """
    Maps GO column to slim GO
    :param godb: The GO database
    :param df_clean: DataFrame with one GO term per row
    :param go_colname: Name for the column with GO terms
    :return: DataFrame with old GO terms replaced with slim GO terms
    """
    df_loc = df_clean.copy()
    func_series = df_loc[go_colname]
    func_set = set(func_series)
    mapper = godb.map_set_to_slim(func_set)
    df_loc.loc[:, (go_colname)] = func_series.map(mapper)
    return df_loc
