code: def _check_existing_logger(loggername, short_name):
      
      if loggername in LOGGERS:
          # Check if short_name matches the existing one, if not update it
          if isinstance(LOGGERS[loggername], BenchLoggerAdapter):
              if ("source" not in LOGGERS[loggername].extra or
                      LOGGERS[loggername].extra["source"] != short_name):
                  LOGGERS[loggername].extra["source"] = short_name
          return LOGGERS[loggername]
      return None
docs: Check if logger with name loggername exists.
  
      :param loggername: Name of logger.
      :param short_name: Shortened name for the logger.
      :return: Logger or None