def METHOD_NAME(self, resources):
    def process_tags(resource):
        client = local_session(self.session_factory).client('glacier')
        tag_dict = self.retry(
            client.list_tags_for_vault,
            vaultName=resource[self.get_model().name])['Tags']
        tag_list = []
        for k, v in tag_dict.items():
            tag_list.append({'Key': k, 'Value': v})
        resource['Tags'] = tag_list
        return resource
    with self.executor_factory(max_workers=2) as w:
        return list(w.map(process_tags, resources))