code: def test_should_respond_200_json(self, url_safe_serializer):
      dagbag = DagBag(dag_folder=EXAMPLE_DAG_FILE)
      dagbag.sync_to_db()
      test_dag: DAG = dagbag.dags[TEST_DAG_ID]
      dag_docstring = self._get_dag_file_docstring(test_dag.fileloc)
  
      url = f"/api/v1/dagSources/{url_safe_serializer.dumps(test_dag.fileloc)}"
      response = self.client.get(
          url,
          headers={"Accept": "application/json"},
          environ_overrides={"REMOTE_USER": "test"},
      )
  
      assert 200 == response.status_code
      assert dag_docstring in response.json["content"]
      assert "application/json" == response.headers["Content-Type"]
  
imports: from __future__ import annotations
  import ast
  import os
  from typing import TYPE_CHECKING
  import pytest
  from airflow.models import DagBag
  from airflow.security import permissions
  from tests.test_utils.api_connexion_utils import assert_401, create_user, delete_user
  from tests.test_utils.db import clear_db_dag_code, clear_db_dags, clear_db_serialized_dags
label_desc: Use image node_id 6 for calling the TestGetSource obj's underlying member method code with example usage: obj.test_should_respond_200_json(url_safe_serializer) without return types