code: def run_backfill(self, dag_id, task_id):
      dag = self.dagbag.get_dag(dag_id)
      dag.clear()
  
      job = Job()
      job_runner = BackfillJobRunner(
          job=job,
          dag=dag,
          start_date=DEFAULT_DATE,
          end_date=DEFAULT_DATE,
      )
      run_job(job=job, execute_callable=job_runner._execute)
      run_id = DagRun.generate_run_id(
          DagRunType.BACKFILL_JOB, execution_date=DEFAULT_DATE
      )
      ti = TaskInstance(task=dag.get_task(task_id), run_id=run_id)
      ti.refresh_from_db()
  
      assert ti.state == State.SUCCESS
  
imports: from __future__ import annotations
  import contextlib
  import logging
  import os
  import subprocess
  import sys
  import tempfile
  from pathlib import Path
  import pytest
  from airflow.configuration import conf
  from airflow.jobs.backfill_job_runner import BackfillJobRunner
  from airflow.jobs.job import Job, run_job
  from airflow.models import DagBag, DagRun, TaskInstance
  from airflow.utils.db import add_default_pool_if_not_exists
  from airflow.utils.state import State
  from airflow.utils.timezone import datetime
  from airflow.utils.types import DagRunType
  from tests.test_utils import db
label_desc: Use image node_id 3 for calling the BaseImpersonationTest obj's underlying member method code with example usage: obj.run_backfill(dag_id, task_id) without return types