code: def get_selected_tab(self):
          
          selected = self.request.GET.get(self.param_name, None)
          if selected:
              try:
                  tab_group, tab_name = selected.split(SEPARATOR)
              except ValueError:
                  return None
              if tab_group == self.get_id():
                  self._selected = self.get_tab(tab_name)
          return self._selected
docs: Returns the tab specific by the GET request parameter.
  
          In the event that there is no GET request parameter, the value
          of the query parameter is invalid, or the tab is not allowed/enabled,
          the return value of this function is None.