docstr: Callback when the timer finishes.
  Also reschedules the next callback.
code: def _vispy_timeout(self):
      """Callback when the timer finishes.
      Also reschedules the next callback.
      """
      self._vispy_timer._timeout()
      self._id = self._tk.after(self.last_interval, self._vispy_timeout)
  
imports: from __future__ import division
  from time import sleep
  import warnings
  from ..base import BaseApplicationBackend, BaseCanvasBackend, BaseTimerBackend
  from ...util import keys
  from ...util.ptime import time
  from ...gloo import gl
label_desc: Use image node_id 4 for calling the TimerBackend obj's underlying member method code with example usage: obj._vispy_timeout() without return types