code: function(property, value) {
          var values = [];
          for (var i in this._nodes) {
              if (this._nodes.hasOwnProperty(i)) {
                  var n = this._nodes[i];
                  if ((property in n && n[property] == value) || (n.data && value == n.data[property])) {
                      values.push(n);
                  }
              }
          }
  
          return (values.length) ? values : null;
      }
docs: Returns a collection of nodes that have a matching property
  and value in the data object that was passed into its constructor.
  @method getNodesByProperty
  @param {object} property the property to search (usually a string)
  @param {object} value the value we want to find (usuall an int or string)
  @return {Array} the matching collection of nodes, null if no match