docs: def create_completer_query(self, service_name):
          """Create a CompleterDescriber for a service.
  
          :type service_name: str
          :param service_name: The name of the service, e.g. 'ec2'
  
          :return: A CompleterDescriber object.
  
          """
          if service_name not in self._describer_cache:
              query = self._create_completer_query(service_name)
              self._describer_cache[service_name] = query
          return self._describer_cache[service_name]