code: function() {
          if (OpenLayers.Handler.prototype.activate.apply(this, arguments)) {
              this.observeElement = this.observeElement || document;
              for (var i=0, len=this.KEY_EVENTS.length; i<len; i++) {
                  OpenLayers.Event.observe(
                      this.observeElement, this.KEY_EVENTS[i], this.eventListener);
              }
              return true;
          } else {
              return false;
          }
      }
docs: Method: activate