class_docstr: Class to support multiple render passes for a renderer.
  
  Notes
  -----
  Passes are organized here as "primary" (vtkOpenGLRenderPass) that act
  within the renderer and "post-processing" (vtkImageProcessingPass) passes,
  which act on the image generated from the renderer.
  
  The primary passes are added as part of a vtk.vtkRenderPassCollection or
  are "stacked", while the post-processing passes are added as a final pass
  to the rendered image.
  
  Parameters
  ----------
  renderer : vtk.vtkRenderer
      Renderer to initialize render passes for.
docstr: Return the renderer.
docstr_tok: ["Return","the","renderer","."]
code: def _renderer(self):
      """Return the renderer."""
      if self._renderer_ref is not None:
          return self._renderer_ref()
  
imports: import weakref
  from .None import _vtk
label_desc: Use image node_id 6 for calling the RenderPasses obj's underlying member method code with example usage: obj._renderer() and returns: self