code: def test_placeholder_config_from_extra(self):
      conn_params = dict(extra=json.dumps(dict(placeholder="?")))
      hook = self.get_hook(conn_params=conn_params)
      assert hook.placeholder == "?"
  
imports: from __future__ import annotations
  import json
  import logging
  from dataclasses import dataclass
  from unittest import mock
  from unittest.mock import patch
  from urllib.parse import quote_plus, urlsplit
  import pyodbc
  import pytest
  from airflow.models import Connection
  from airflow.providers.odbc.hooks.odbc import OdbcHook
label_desc: Use image node_id 18 for calling the TestOdbcHook obj's underlying member method code with example usage: obj.test_placeholder_config_from_extra() without return types