Line :: visible - Visible property
The property is true, when the attached line is visible, i.e. part of an expanded region. This does not mean, that the line is currently visible in the part of the list displayed, but that it becomes visible, when scrolling the list to the right position.
When the item is not part of an expanded region, the property returns false. When no line is attached, the function throws an exception.
Return value: Check option ( bool )
In order to mark the GUI element as checked, true should be passed. False might be passed in order to reset the check mark in a action item, list entry or check box.