code: def log_once(log_func, msg, *args, **kwargs):
    Logs a message only once."""
    if msg not in _LOG_ONCE_SEEN:
      log_func(msg, *args, **kwargs)
      # Key on the message, ignoring args. This should fit most use cases.
      _LOG_ONCE_SEEN.add(msg)
docs: Logs a message only once.