class_docstr: SDL2 backend for Canvas abstract class.
class_docstr_tok: ["SDL2","backend","for","Canvas","abstract","class","."]
code: def _vispy_update(self):
      # Invoke a redraw, passing it on to the canvas
      if self._vispy_canvas is None or self._id is None:
          return
      # Mark that this window wants to be drawn on the next loop iter
      self._needs_draw = True
  
imports: from __future__ import division
  import atexit
  import ctypes
  from time import sleep
  import warnings
  import gc
  from ..base import BaseApplicationBackend, BaseCanvasBackend, BaseTimerBackend
  from ...util import keys, logger
  from ...util.ptime import time
  from ...None import config
label_desc: Use image node_id 9 for calling the CanvasBackend obj's underlying member method code with example usage: obj._vispy_update() without return types