code: def test_download_line_items_should_be_called_once(
      self, get_conn_mock
  ):
      request_body = {
          "filterType": "filter_type",
          "filterIds": [],
          "format": "format",
          "fileSpec": "file_spec",
      }
      self.hook.download_line_items(request_body=request_body)
      get_conn_mock.return_value.lineitems.return_value.downloadlineitems.assert_called_once()
  
imports: from __future__ import annotations
  from unittest import mock
  from airflow.providers.google.marketing_platform.hooks.display_video import GoogleDisplayVideo360Hook
  from tests.providers.google.cloud.utils.base_gcp_mock import mock_base_gcp_hook_default_project_id
label_desc: Use image node_id 9 for calling the TestGoogleDisplayVideo360Hook obj's underlying member method code with example usage: obj.test_download_line_items_should_be_called_once(get_conn_mock) without return types