class_docstr: OpenAPIServiceConnector connects to OpenAPI services, allowing for the invocation of methods specified in
  an OpenAPI specification of that service. It integrates with ChatMessage interface, where messages are used to
  determine the method to be called and the parameters to be passed. The message payload should be a JSON formatted
  string consisting of the method name and the parameters to be passed to the method. The method name and parameters
  are then used to invoke the method on the OpenAPI service. The response from the service is returned as a
  ChatMessage.
  
  Before using this component, one needs to register functions from the OpenAPI specification with LLM.
  This can be done using the OpenAPIServiceToFunctions component.
docstr: Authenticates with the OpenAPI service if required.
  
  :param openapi_service: The OpenAPI service instance.
  :type openapi_service: OpenAPI
  :raises ValueError: If authentication fails or is not found.
code: def _authenticate_service(self, openapi_service: OpenAPI):
      """
      Authenticates with the OpenAPI service if required.
  
      :param openapi_service: The OpenAPI service instance.
      :type openapi_service: OpenAPI
      :raises ValueError: If authentication fails or is not found.
      """
      if openapi_service.components.securitySchemes:
          auth_method = list(
              openapi_service.components.securitySchemes.keys()
          )[0]
          service_title = openapi_service.info.title
          if service_title not in self.service_authentications:
              raise ValueError(
                  f"Service {service_title} not found in service_authentications."
              )
          openapi_service.authenticate(
              auth_method, self.service_authentications[service_title]
          )
  
file_path: haystack/haystack/components/connectors/openapi_service.py
imports: import json
  import logging
  from typing import List, Dict, Any, Optional
  from haystack import component
  from haystack.dataclasses import ChatMessage, ChatRole
  from haystack.lazy_imports import LazyImport
label_desc: Use image node_id 4 for calling the OpenAPIServiceConnector obj's underlying member method code with example usage: obj._authenticate_service(openapi_service) without return types