class_docstr: OSMesa backend for Canvas
class_docstr_tok: ["OSMesa","backend","for","Canvas"]
code: def _vispy_close(self):
      if self.closed:
          return
      # We do not set self._native_context = None here because this causes
      # trouble in case a canvas is closed multiple times (as in
      # app.test_run()). The problem occurs in gloo's glir._gl_initialize
      # when it tries to call glGetString(GL_VERSION).
      # But OSMesa requires a context to be attached when calling
      # glGetString otherwise it returns an empty string, which gloo doesn't
      # like
      self._closed = True
      return
  
imports: from __future__ import division
  from ...util.ptime import time
  from ..base import BaseApplicationBackend, BaseCanvasBackend, BaseTimerBackend
  from ...gloo import gl
  from time import sleep
label_desc: Use image node_id 10 for calling the CanvasBackend obj's underlying member method code with example usage: obj._vispy_close() without return types