Why Python Pyside2 about QScrollBar's handle set-height not ok?

Sorry, I was asking the same question,about Python Pyside2 ;
why Python Pyside2 about QScrollBar’s handle set-height not ok?
QScrollBar’s handle height of the document to which it is written varies according to the content of the page,and don’t re-layout……Unless you redefine the rules

So, how do I define it?