def rename_columns(df, rename_dict):
    """Renames columns based on `rename_dict`

    Args:
        df (`pandas.DataFrame`): The dataframe to rename columns in
        rename_dict (:type:`dict`): A dict in the format `{'old_name': 'new_name'}`
            to use to rename the columns

    Returns:
        `pandas.DataFrame`: `df` with renamed columns
    """

    return df.rename(columns=rename_dict)