code: function (eventName, handler) {
      this._validateEvent(eventName);
      var hl = this._handlers[eventName].length;
      for (var i=0;i<hl;i++) {
        if (this._handlers[eventName][i] === handler) {
          this._handlers[eventName].splice(i, 1);
          return;
        }
      }
    }
docs: Remove a previously installed event handler