code: def test_extra_links(self):
      provider_manager = ProvidersManager()
      extra_link_class_names = list(
          provider_manager.extra_links_class_names
      )
      assert len(extra_link_class_names) > 6
  
imports: from __future__ import annotations
  import logging
  import re
  import sys
  from unittest.mock import patch
  import pytest
  from flask_appbuilder.fieldwidgets import BS3TextFieldWidget
  from flask_babel import lazy_gettext
  from wtforms import BooleanField, Field, StringField
  from airflow.exceptions import AirflowOptionalProviderFeatureException
  from airflow.providers_manager import HookClassProvider, LazyDictWithCache, PluginInfo, ProviderInfo, ProvidersManager
label_desc: Use image node_id 18 for calling the TestProviderManager obj's underlying member method code with example usage: obj.test_extra_links() without return types