def display_popup(self, title, content):
        """
        Display a pop-up dialog.
        """
        assert isinstance(title, six.text_type)
        assert isinstance(content, six.text_type)

        self.popup_dialog.title = title
        self._popup_textarea.text = content
        self.client_state.display_popup = True
        get_app().layout.focus(self._popup_textarea)
Display a pop-up dialog.