code: def _update_opacity(self):
      self._opacity_filter.alpha = self._opacity
      self.update()
  
file_path: vispy/vispy/scene/visuals.py
imports: import re
  import weakref
  from ..None import visuals
  from .node import Node
  from ..visuals.filters import Alpha, PickingFilter
  from typing import TypeVar
label_desc: Use image node_id 2 for calling the VisualNode obj's underlying member method code with example usage: obj._update_opacity() without return types