code: function (obj, obj2, data) {
      if(!this.hasNode(obj.id)) { this.addNode(obj); }
      if(!this.hasNode(obj2.id)) { this.addNode(obj2); }
      obj = this.nodes[obj.id]; obj2 = this.nodes[obj2.id];
      var adjsObj = this.edges[obj.id] = this.edges[obj.id] || {};
      var adjsObj2 = this.edges[obj2.id] = this.edges[obj2.id] || {};
      adjsObj[obj2.id] = adjsObj2[obj.id] = new Graph.Adjacence(obj, obj2, data, this.Edge, this.Label);
      return adjsObj[obj2.id];
   }
docs: /*
  Method: addAdjacence
  
  Connects nodes specified by *obj* and *obj2*. If not found, nodes are created.
  
  Parameters:
  
  obj - (object) A <Graph.Node> object.
  obj2 - (object) Another <Graph.Node> object.
  data - (object) A data object. Used to store some extra information in the <Graph.Adjacence> object created.
  
  See also:
  
  <Graph.Node>, <Graph.Adjacence>