'Override filter_all() which operates on the full list
of cells...'

def filter_all(self, cells, filter_properties):

    scheduler_hints = filter_properties.get('scheduler_hints')
    if (not scheduler_hints):
        return cells
    cell_name = scheduler_hints.pop('target_cell', None)
    if (not cell_name):
        return cells
    if (not self.authorized(filter_properties['context'])):
        return cells
    LOG.info("Forcing    direct    route    to    %(cell_name)s    because    of    'target_cell'    scheduler    hint", {'cell_name': cell_name})
    scheduler = filter_properties['scheduler']
    if (cell_name == filter_properties['routing_path']):
        return [scheduler.state_manager.get_my_state()]
    ctxt = filter_properties['context']
    scheduler.msg_runner.build_instances(ctxt, cell_name, filter_properties['host_sched_kwargs'])
