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.

def assert_condition_last_modified(self):
        """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.
        """
        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.')