python3-sentinels 1.0.0-4 (amd64 binary) in ubuntu eoan

 Sentinels are objects with special meanings that can be passed as meaningful
 flags rather than special casing 0, None, -1, False etc. Sentinels can be
 thought of as singletons, but they service the need of having 'special'
 values in code,
 .
 This package contains the Python 3 version of the sentinels module.