Sentinel ======== This is a small class that improves upon using a plain object as a sentinel for function arguments when None is a valid parameter and can't be used as the default. The improvements vs. a plain object are: * Better ``__str__`` and ``__repr__`` for better messages in logs and stacktraces. Instead of something like ``''`` you get ``''`` * Sentinels are picklable See: https://en.wikipedia.org/wiki/Sentinel_value Inspired by: https://pypi.org/project/sentinels/ .. autoclass:: collections_extended.sentinel