code: def setArrowStyle( self, state ):
          
          self._arrowStyle = state
          
          if not state:
              self.setStyleSheet('')
          else:
              right = resources.find('img/treeview/triangle_right.png')
              down  = resources.find('img/treeview/triangle_down.png')
              opts  = (right.replace('\\', '/'), down.replace('\\', '/'))
              self.setStyleSheet(ARROW_STYLESHEET % opts)
docs: Sets whether or not to use arrows for the grouping mechanism.
          
          :param      state | <bool>