code: def add_widget(self, widget):
          
          if self._buttons.get(widget):
              return
          btn = self.create_button(widget)
          cb = partial(self.focus_widget, w=widget)
          btn.clicked.connect(cb)
          self.layout().addWidget(btn)
          self._buttons[widget] = btn
docs: Add the given widget to the tooltip
  
          :param widget: the widget to add
          :type widget: QtGui.QWidget
          :returns: None
          :rtype: None
          :raises: None