code: function( evt ) {
  			var undoManager = this.undoManager,
  				keyCode = evt.data.getKey(),
  				totalInputs = this.keyEventsStack.getTotalInputs();
  
  			// Remove record from stack for provided key code.
  			this.keyEventsStack.remove( keyCode );
  
  			// Second part of the workaround for IEs functional keys bug. We need to check whether something has really
  			// changed because we blindly mocked the keypress event.
  			// Also we need to be aware that lastKeydownImage might not be available (#12327).
  			if ( UndoManager.ieFunctionalKeysBug( keyCode ) && this.lastKeydownImage &&
  				this.lastKeydownImage.equalsContent( new Image( undoManager.editor, true ) ) ) {
  				return;
  			}
  
  			if ( totalInputs > 0 ) {
  				undoManager.type( keyCode );
  			} else if ( UndoManager.isNavigationKey( keyCode ) ) {
  				// Note content snapshot has been checked in keydown.
  				this.onNavigationKey( true );
  			}
  		}
docs: The `keyup` event listener.
  
  @param {CKEDITOR.dom.event} evt