code: def test_response_409(self, session):
      pool_name = "test_pool_a"
      pool_instance = Pool(
          pool=pool_name, slots=3, include_deferred=False
      )
      session.add(pool_instance)
      session.commit()
      response = self.client.post(
          "api/v1/pools",
          json={
              "name": "test_pool_a",
              "slots": 3,
              "include_deferred": False,
          },
          environ_overrides={"REMOTE_USER": "test"},
      )
      assert response.status_code == 409
      assert {
          "detail": f"Pool: {pool_name} already exists",
          "status": 409,
          "title": "Conflict",
          "type": EXCEPTIONS_LINK_MAP[409],
      } == response.json
  
imports: from __future__ import annotations
  import pytest
  from airflow.api_connexion.exceptions import EXCEPTIONS_LINK_MAP
  from airflow.models.pool import Pool
  from airflow.security import permissions
  from airflow.utils.session import provide_session
  from tests.test_utils.api_connexion_utils import assert_401, create_user, delete_user
  from tests.test_utils.config import conf_vars
  from tests.test_utils.db import clear_db_pools
label_desc: Use image node_id 2 for calling the TestPostPool obj's underlying member method code with example usage: obj.test_response_409(session) without return types