def rename_columns(df):
    """
    Renames the columns of the data frame

    Parameters
    ----------
    df : pandas data frame
        The building benchmarking data for a city

    Returns
    ----------
    df
        The modified data frame
    """

    df.rename({'zip': 'ZIPCode',
               'utility_name': 'UtilityCompany',
               'state': 'State',
               'service_type': 'ServiceType',
               'ownership': 'Ownership',
               'commercial_rate': 'CommercialRate',
               'industrial_rate': 'IndustrialRate',
               'residential_rate': 'ResidentialRate'
               }, axis=1, inplace=True)

    return df