code: function() {
      if (this.handler) {
        this.handler();
        if (mindmaps.DEBUG) {
          console.log("handler called for", this.id);
        }
      } else {
        if (mindmaps.DEBUG) {
          console.log("no handler found for", this.id);
        }
      }
    }
docs: Executes the command. Tries to call the handler function.