code: function() {
  
          this.vel.empty();
          this._V = {};
          this.renderMarkup();
          // rendering labels has to be run after the link is appended to DOM tree. (otherwise <Text> bbox
          // returns zero values)
          this.renderLabels();
          // start watching the ends of the link for changes
          var model = this.model;
          this.watchSource(model, model.source())
              .watchTarget(model, model.target())
              .update();
  
          return this;
      }
docs: Rendering. ----------