code: function(filter) {
          if(filter.filters) {
              for(var i=0, len=filter.filters.length; i<len; ++i) {
                  OpenLayers.Format.WFST.v1.prototype.setFilterProperty.call(this, filter.filters[i]);
              }
          } else {
              if(filter instanceof OpenLayers.Filter.Spatial && !filter.property) {
                  // got a spatial filter without property, so set it
                  filter.property = this.geometryName;
              }
          }
      }
docs: Method: setFilterProperty
  Set the property of each spatial filter.
  
  Parameters:
  filter - {<OpenLayers.Filter>}