code: def test_custom_template_loader(client):
      class MyFlask(flask.Flask):
          def create_global_jinja_loader(self):
              from jinja2 import DictLoader
  
              return DictLoader({"index.html": "Hello Custom World!"})
  
      app = MyFlask(__name__)
  
      @app.route("/")
      def index():
          return flask.render_template("index.html")
  
      c = app.test_client()
      rv = c.get("/")
      assert rv.data == b"Hello Custom World!"
  
imports: import logging
  import pytest
  import werkzeug.serving
  from jinja2 import TemplateNotFound
  from markupsafe import Markup
  import flask
label_desc: Use image node_id 27 for calling a global function with example usage: test_custom_template_loader(client) and returns: flask, DictLoader