code: def _open_fbdev(fbdev=None):
          
          dev = fbdev or os.getenv('FRAMEBUFFER', '/dev/fb0')
          fbfid = os.open(dev, os.O_RDWR)
          return fbfid
docs: Return the framebuffer file descriptor.
  
          Try to use the FRAMEBUFFER
          environment variable if fbdev is not given. Use '/dev/fb0' by
          default.