code: def assert_condition_last_modified(self):
          
          rq = self.request
          rs = self.response
          if rs.last_modified:
              rsl = rs.last_modified
              if rq.if_modified_since and rsl <= rq.if_modified_since:
                  raise_304(self)
              if rq.if_unmodified_since and rsl > rq.if_unmodified_since:
                  raise_412(self, 'Resource is newer than the '
                      'If-Unmodified-Since request header.')
docs: If the resource has a last modified date (see
          :func:`get_last_modified`) the request headers ``If-Modified-Since``
          and ``If-Unmodified-Since`` are verified. May abort the request with
          304 or 412 response codes.
  
          :raises:
              - :class:`webob.exceptions.ResponseException` of status 304 if the
                ``If-Modified-Since`` is later than the last modified date.
              - :class:`webob.exceptions.ResponseException` of status 412 if the
                last modified date is later than the ``If-Unmodified-Since``
                header.