old_contents: class NoCache(object):
      """
      A cache implementation that never caches.
      """
      def getCache(self, service, url, headers):
          return None
  
      def processResponse(self, service, url, response):
          pass
  
new_contents: class NoCache(object):
      """
      A cache implementation that never caches.
      """
      def getCache(self, service, url, headers):
          return None
  
      def processResponse(self, service, url, response):
          pass
  
      def deleteCache(self, service, url):
          pass
  
subject: Add deleteCache method