code: def test_handler(gather_mock):
      """StreamAlertApp Lambda - Test Handler"""
      app_type = "duo_auth"
      event = get_event(app_type)
      put_mock_params(app_type)
      handler(event, get_mock_lambda_context(app_type))
      gather_mock.assert_called_once()
  
imports: import os
  from mock import patch
  from moto import mock_ssm
  from streamalert.apps.main import handler
  from tests.unit.streamalert.apps.test_helpers import get_event, put_mock_params
  from tests.unit.streamalert.shared.test_config import get_mock_lambda_context
label_desc: Use image node_id 1 for calling a global function with example usage: test_handler(gather_mock) without return types