code: def setJoiner(self, joiner):
          
          text = QueryCompound.Op[joiner].upper()
          
          if self._first:
              if self._last:
                  self.uiJoinSBTN.setCurrentAction(None)
              else:
                  act = self.uiJoinSBTN.findAction(text)
                  self.uiJoinSBTN.setCurrentAction(act)
          else:
              self.uiJoinSBTN.actions()[0].setText(text)
docs: Sets the join operator type for this entry widget to the given value.
          
          :param      joiner | <QueryCompound.Op>