code: def startDrag( self, supportedActions ):
          
          if ( not self.useDragPixmaps() ):
              return super(XTreeWidget, self).startDrag(supportedActions)
          
          filt  = lambda x: x.flags() & QtCore.Qt.ItemIsDragEnabled
          items = filter(filt, self.selectedItems())
          if ( not items ):
              return
          
          data = self.mimeData(items)
          if ( not data ):
              return
          
          if ( len(items) > 1 ):
              pixmap = self.dragMultiPixmap()
          else:
              pixmap = self.dragSinglePixmap()
          
          # create the drag event
          drag = QtGui.QDrag(self)
          drag.setMimeData(data)
          drag.setPixmap(pixmap)
          
          drag.exec_(supportedActions, QtCore.Qt.MoveAction)
docs: Starts a new drag event for this tree widget.  Overloading from the
          default QTreeWidget class to define a better pixmap option when
          dragging many items.
          
          :param      supportedActions | <QtCore.Qt.DragActions>