def cleanstrings_snake(df, cols):
    """Clean the strings in a columns in a dataframe with snake case.

    Args:
        df (panda.DataFrame) : original dataframe.
        cols (list): list of columns in `df` to apply snake case to.

    """
    for col in cols:
        df.loc[:, col] = (
            df[col]
            .astype(str)
            .str.strip()
            .str.lower()
            .str.replace(r"\s+", "_", regex=True)
        )
    return df