docs: def describe_autocomplete(self, service, operation, param):
          """Describe operation and args needed for server side completion.
  
          :type service: str
          :param service: The AWS service name.
  
          :type operation: str
          :param operation: The AWS operation name.
  
          :type param: str
          :param param: The name of the parameter being completed.  This must
              match the casing in the service model (e.g. InstanceIds, not
              --instance-ids).
  
          :rtype: ServerCompletion
          :return: A ServerCompletion object that describes what API call to make
              in order to complete the response.
  
          """
          service_index = self._index[service]
          LOG.debug(service_index)
          if param not in service_index.get('operations', {}).get(operation, {}):
              LOG.debug("param not in index: %s", param)
              return None
          p = service_index['operations'][operation][param]
          resource_name = p['resourceName']
          resource_identifier = p['resourceIdentifier']
  
          resource_index = service_index['resources'][resource_name]
          completion_operation = resource_index['operation']
          path = resource_index['resourceIdentifier'][resource_identifier]
          return ServerCompletion(service=service, operation=completion_operation,
                                  params={}, path=path)