def test_iadd(self, evt):
        rval = event.ReturnValue(append_events=[evt])
        rval2 = event.ReturnValue(eat=True, append_events=[evt])
        rset = event.ResultSet()

        rset += rval
        rset += rval2
        rset += None
        assert rset.eat
        assert rset.append_events == [evt, evt]
def main(self):
      UI.OpenDialog(
        VBox(
          Heading("This Is a Heading."),
          Label("This is a Label."),
          PushButton("&OK")
        )
      )
      UI.UserInput()
      UI.CloseDialog()