code: def get_conv_widget(self, conv_id):
          
          if conv_id not in self._conv_widgets:
              set_title_cb = (lambda widget, title:
                              self._tabbed_window.set_tab(widget, title=title))
              widget = ConversationWidget(
                  self._client, self._coroutine_queue,
                  self._conv_list.get(conv_id), set_title_cb, self._keys,
                  self._datetimefmt
              )
              self._conv_widgets[conv_id] = widget
          return self._conv_widgets[conv_id]
docs: Return an existing or new ConversationWidget.