set_expander_column
Description:
Sets the column to draw the expander arrow at.
Note: 
      
        
    
    Use [class@Gtk.ListView] or [class@Gtk.ColumnView] instead
 It must be in this. If column is null, then the expander 
      arrow is always at the first visible column.
If you do not want expander arrow to appear in your tree, set the expander column to a hidden column.
Parameters:
| this | A `GtkTreeView` | 
| column | null, or the column to draw the expander arrow at. |