code: def setup(app):
      """Setup plugin"""
      app.connect("build-finished", build_postprocess)
  
      app.add_config_value(
          "html_extra_with_substitutions", [], "html", [str]
      )
      app.add_config_value(
          "manual_substitutions_in_generated_html", [], "html", [str]
      )
      app.add_config_value("global_substitutions", {}, "html", [dict])
  
      return {
          "parallel_write_safe": True,
          "parallel_read_safe": True,
      }
  
imports: from __future__ import annotations
  import os
label_desc: Use image node_id 3 for calling a global function with example usage: setup(app) and returns: dict