code: def test_invoke_method_valid(self, connector, openapi_service_mock):
      # Test valid method invocation
      method_invocation_descriptor = {
          "name": "test_method",
          "arguments": {},
      }
      openapi_service_mock.call_test_method = Mock(
          return_value="response"
      )
      result = connector._invoke_method(
          openapi_service_mock, method_invocation_descriptor
      )
      assert result == "response"
  
file_path: haystack/test/components/connectors/test_openapi_service.py
imports: import json
  import pytest
  from unittest.mock import MagicMock, Mock
  from openapi3 import OpenAPI
  from haystack.components.connectors import OpenAPIServiceConnector
  from haystack.dataclasses import ChatMessage
label_desc: Use image node_id 6 for calling the TestOpenAPIServiceConnector obj's underlying member method code with example usage: obj.test_invoke_method_valid(connector, openapi_service_mock) without return types