code: def setup(app):
      """Required Sphinx extension setup function."""
      app.add_node(bokeh_palette_group, html=bokeh_palette_group.html)
      app.add_directive(
          "bokeh-palette-group", BokehPaletteGroupDirective
      )
  
      return PARALLEL_SAFE
  
file_path: bokeh/src/bokeh/sphinxext/bokeh_palette_group.py
imports: from __future__ import annotations
  import logging
  from docutils import nodes
  from docutils.parsers.rst import Directive
  from sphinx.errors import SphinxError
  import bokeh.palettes
  from .None import PARALLEL_SAFE
  from .templates import PALETTE_GROUP_DETAIL
label_desc: Use image node_id 1 for calling a global function with example usage: setup(app) and returns: PARALLEL_SAFE