code: function(entities, options) {
        options = langx.mixin({}, options);
        var singular = !langx.isArray(entities);
        entities = singular ? [entities] : entities.slice();
        var removed = this._removeEntitys(entities, options);
        if (!options.silent && removed.length) {
          options.changes = {added: [], merged: [], removed: removed};
          this.trigger('update', this, options);
        }
        return singular ? removed[0] : removed;
      }
docs: Remove a entity, or a list of entities from the set.