code: function(features) {
          if(!(OpenLayers.Util.isArray(features))) {
              features = [features];
          }
          var gml = this.createElementNS("http://www.opengis.net/wfs",
                                         "wfs:" + this.collectionName);
          for(var i=0; i<features.length; i++) {
              gml.appendChild(this.createFeatureXML(features[i]));
          }
          return OpenLayers.Format.XML.prototype.write.apply(this, [gml]);
      }
docs: APIMethod: write
  Generate a GML document string given a list of features.
  
  Parameters:
  features - {Array(<OpenLayers.Feature.Vector>)} List of features to
  serialize into a string.
  
  Returns:
  {String} A string representing the GML document.