JToolBarHelper::cancel('mycomponent.cancel', 'Cancel');This code will add a button labeled "Cancel" to the toolbar, which when clicked will navigate the user back to the previous page without saving any changes. The "mycomponent.cancel" parameter is used to define the name of the task to execute when the button is clicked. This can be used to customize the functionality of the cancel button for each use case. JToolBarHelper is part of the Joomla framework and is included in the Joomla Platform library.