def clean_sts(df):
    """Drop columns containing irrelevant metadata and
    save as new csv files in the target_dir.

    Args:
        df (pandas.Dataframe): drop columns from train/test/dev files.
    """
    clean_df = df.drop(["column_0", "column_1", "column_2", "column_3"], axis=1)
    clean_df = clean_df.rename(
        index=str, columns={"column_4": "score", "column_5": "sentence1", "column_6": "sentence2"}
    )
    return clean_df