docs: def vert_tab_pos(self, positions):
          '''Sets tab positions, up to a maximum of 32 positions. Also can clear tab positions.
          
          Args:
              positions -- Either a list of tab positions (between 1 and 255), or 'clear'.
          Returns:
              None
          Raises:
              RuntimeError: Invalid position parameter.
              RuntimeError: Too many positions.
          '''
          if positions == 'clear':
              self.send(chr(27)+'B'+chr(0))
              return
          if positions.min < 1 or positions.max >255:
                  raise RuntimeError('Invalid position parameter in function horzTabPos')
          sendstr = chr(27) + 'D'
          if len(positions)<=16:
              for position in positions:
                  sendstr += chr(position)
              self.send(sendstr + chr(0))
          else:
              raise RuntimeError('Too many positions in function vertTabPos')