code: def test_jinja_extension_installed(self):
      install_translations(self.env, parse_locale("en"), [])
      self.env.add_extension.assert_called_once_with("jinja2.ext.i18n")
  
file_path: mkdocs/mkdocs/tests/localization_tests.py
imports: import unittest
  from unittest import mock
  from mkdocs.config.base import ValidationError
  from mkdocs.localization import install_translations, parse_locale
  from mkdocs.tests.base import tempdir
label_desc: Use image node_id 2 for calling the LocalizationTests obj's underlying member method code with example usage: obj.test_jinja_extension_installed() without return types