'Starts interactive animation. Adds the draw frame command to the GUI
handler, calls show to start the event loop.'

def _start(self, *args):

    self._fig.canvas.mpl_disconnect(self._first_draw_id)
    self._first_draw_id = None
    self._init_draw()
    self.event_source.add_callback(self._step)
    self.event_source.start()
