QTreeView switch tab positions

Question

I have a qt object QTreeView and I want to switch tab positions. Basicly i have a filled TreeView. And the function

columnViewportPosition ( int column ) 

returns 0 for the first column and let's say 50 for the second. I want to switch them so that the are displayed in a different order, so that columnViewportPosition would return 50 for the first column and 0 for the second. How do i do that?