<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 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)