'Animate the bubble into position'

def show(self, pos, duration, width=None, modal=False, exit=False):

    (self.modal, self.exit) = (modal, exit)
    if width:
        self.width = width
    if self.modal:
        from kivy.uix.modalview import ModalView
        self._modal_view = m = ModalView(background_color=[0.5, 0.5, 0.5, 0.2])
        Window.add_widget(m)
        m.add_widget(self)
    else:
        Window.add_widget(self)
    Clock.schedule_once((lambda dt: self._show(pos, duration)))
