code: def show_info(self):
          
  
          sender = self.sender()
          tree = sender.parent()
          index = tree.selectedIndexes()
          info = ''
          if index != []:
              index = index[0]
              name = str(index.model().itemFromIndex(index).text())
  
              if name in set(list(self.elements_from_file.keys()) + list(self.elements_selected.keys())):
                  probe_name = None
                  instrument_name = name
              else:
                  instrument_name = str(index.model().itemFromIndex(index).parent().text())
                  probe_name = name
  
  
  
              module = __import__('pylabcontrol.instruments', fromlist=[instrument_name])
              if probe_name is None:
                  info = getattr(module, instrument_name).__doc__
              else:
                  if probe_name in list(getattr(module, instrument_name)._PROBES.keys()):
                      info = getattr(module, instrument_name)._PROBES[probe_name]
  
          if info is not None:
              self.lbl_info.setText(info)
docs: displays the doc string of the selected element