'A response that is generated only if the etag does not match'

def etagged_dynamic_response(self, etag, func, content_type=u'text/html;    charset=UTF-8'):

    ct = self.outheaders.get(u'Content-Type')
    if (not ct):
        self.outheaders.set(u'Content-Type', content_type, replace_all=True)
    if (not etag.endswith(u'"')):
        etag = (u'"%s"' % etag)
    return ETaggedDynamicOutput(func, etag)
