code: def clean_db():
      clear_db_runs()
      clear_db_pools()
      clear_db_dags()
      clear_db_sla_miss()
      clear_db_import_errors()
      clear_db_jobs()
      clear_db_serialized_dags()
  
imports: from __future__ import annotations
  import datetime
  import os
  from unittest import mock
  from unittest.mock import MagicMock, patch
  from zipfile import ZipFile
  import pytest
  from airflow import PY311, settings
  from airflow.callbacks.callback_requests import TaskCallbackRequest
  from airflow.configuration import TEST_DAGS_FOLDER, conf
  from airflow.dag_processing.manager import DagFileProcessorAgent
  from airflow.dag_processing.processor import DagFileProcessor, DagFileProcessorProcess
  from airflow.models import DagBag, DagModel, SlaMiss, TaskInstance, errors
  from airflow.models.serialized_dag import SerializedDagModel
  from airflow.models.taskinstance import SimpleTaskInstance
  from airflow.operators.empty import EmptyOperator
  from airflow.utils import timezone
  from airflow.utils.session import create_session
  from airflow.utils.state import State
  from airflow.utils.types import DagRunType
  from tests.test_utils.config import conf_vars, env_vars
  from tests.test_utils.db import clear_db_dags, clear_db_import_errors, clear_db_jobs, clear_db_pools, clear_db_runs, clear_db_serialized_dags, clear_db_sla_miss
  from tests.test_utils.mock_executor import MockExecutor
label_desc: Use image node_id 1 for calling the TestDagFileProcessor obj's underlying member method code with example usage: obj.clean_db() without return types