code: def test_host_key(self, get_connection):
      connection = Connection(
          login="login",
          host="host",
          extra=json.dumps({"host_key": TEST_HOST_KEY}),
      )
      get_connection.return_value = connection
      hook = SFTPHook()
      assert hook.host_key.get_base64() == TEST_HOST_KEY
  
imports: from __future__ import annotations
  import json
  import os
  import shutil
  from io import StringIO
  from unittest import mock
  import paramiko
  import pytest
  from airflow.exceptions import AirflowException, AirflowProviderDeprecationWarning
  from airflow.models import Connection
  from airflow.providers.sftp.hooks.sftp import SFTPHook
  from airflow.providers.ssh.hooks.ssh import SSHHook
  from airflow.utils.session import provide_session
label_desc: Use image node_id 20 for calling the TestSFTPHook obj's underlying member method code with example usage: obj.test_host_key(get_connection) without return types