code: function(metadata) {
          var types = ['name', 'desc', 'author'],
              node = this.createElementNS(this.namespaces.gpx, 'metadata');
          for (var i=0; i < types.length; i++) {
              var type = types[i];
              if (metadata[type]) {
                  var n = this.createElementNS(this.namespaces.gpx, type);
                  n.appendChild(this.createTextNode(metadata[type]));
                  node.appendChild(n);
              }
          }
          return node;
      }
docs: Method: buildMetadataNode
  Creates a "metadata" node.
  
  Returns:
  {DOMElement}