code: function(obj, prop) {
          var node = null;
          if(obj[prop] != null) {
              node = this.createElementNS(this.namespaces.ol, "ol:" + prop);
              node.appendChild(this.createTextNode(obj[prop].toString()));
          }
          return node;
      }
docs: Method: createOLPropertyNode
  Create a node representing an OpenLayers property.  If the property is
  null or undefined, null will be returned.
  
  Parameters:
  obj - {Object} An object.
  prop - {String} A property.
  
  Returns:
  {Element} A property node.