code: def config_loader(app, **kwargs_config):
      
      # This is the only place customize the Flask application right after
      # it has been created, but before all extensions etc are loaded.
      local_templates_path = os.path.join(app.instance_path, 'templates')
      if os.path.exists(local_templates_path):
          # Let's customize the template loader to look into packages
          # and application templates folders.
          app.jinja_loader = ChoiceLoader([
              FileSystemLoader(local_templates_path),
              app.jinja_loader,
          ])
  
      app.jinja_options = dict(
          app.jinja_options,
          cache_size=1000,
          bytecode_cache=BytecodeCache(app)
      )
  
      invenio_config_loader(app, **kwargs_config)
docs: Configuration loader.
  
      Adds support for loading templates from the Flask application's instance
      folder (``<instance_folder>/templates``).