docs: function(entity, options) {
        options = options ? langx.clone(options) : {};
        var wait = options.wait;
        entity = this._prepareEntity(entity, options);
        if (!entity) return false;
        if (!wait) this.add(entity, options);
        var collection = this;
        var success = options.success;
        options.success = function(m, resp, callbackOpts) {
          if (wait) collection.add(m, callbackOpts);
          if (success) success.call(callbackOpts.context, m, resp, callbackOpts);
        };
        entity.save(null, options);
        return entity;
      }