code: function() {
          var filter = new OpenLayers.Filter.FeatureId();
          OpenLayers.Util.extend(filter, this);
          filter.fids = this.fids.slice();
          return filter;
      }
docs: APIMethod: clone
  Clones this filter.
  
  Returns:
  {<OpenLayers.Filter.FeatureId>} Clone of this filter.