If a city shall impose the provisions authorized by Kan. Stat. Ann. § 12-2003, the city shall thereby be deemed to have agreed to hold and save harmless the water corporation from any loss or liability not occasioned by the negligence of such corporation in billing and collecting such sewer service charges, and the city shall defend the water corporation at the expense of the city in any action at law or in equity that may be brought against the water corporation arising out of or claimed to have arisen out of the billing and collection of sewer service charges pursuant to the terms of the franchise.