def _set_metadata(self, req, id, body):
        """Replaces the aggregate's existing metadata with new metadata."""
        context = _get_context(req)
        authorize(context)

        if len(body) != 1:
            raise exc.HTTPBadRequest()
        try:
            metadata = body["metadata"]
        except __HOLE__:
            raise exc.HTTPBadRequest()

        # The metadata should be a dict
        if not isinstance(metadata, dict):
            msg = _('The value of metadata must be a dict')
            raise exc.HTTPBadRequest(explanation=msg)
        try:
            for key, value in metadata.items():
                utils.check_string_length(key, "metadata.key", 1, 255)
                if value is not None:
                    utils.check_string_length(value, "metadata.value", 0, 255)
        except exception.InvalidInput as e:
            raise exc.HTTPBadRequest(explanation=e.format_message())
        try:
            aggregate = self.api.update_aggregate_metadata(context,
                                                           id, metadata)
        except exception.AggregateNotFound:
            msg = _('Cannot set metadata %(metadata)s in aggregate'
                    ' %(id)s') % {'metadata': metadata, 'id': id}
            raise exc.HTTPNotFound(explanation=msg)
        except exception.InvalidAggregateAction as e:
            raise exc.HTTPBadRequest(explanation=e.format_message())

        return self._marshall_aggregate(aggregate)
dataset/ETHPy150Open BU-NU-CLOUD-SP16/Trusted-Platform-Module-nova/nova/api/openstack/compute/legacy_v2/contrib/aggregates.py/AggregateController._set_metadata