code: def on_builder_inited(app):
      
      app.cache_db_path = ":memory:"
      if app.config["uqbar_book_use_cache"]:
          logger.info(bold("[uqbar-book]"), nonl=True)
          logger.info(" initializing cache db")
          app.connection = uqbar.book.sphinx.create_cache_db(app.cache_db_path)
docs: Hooks into Sphinx's ``builder-inited`` event.