old_contents: # flake8: noqa
  from .implicit import implicit
  from .registry import Registry, CachingKeyLookup, Lookup
  from .dispatch import dispatch
  from .mapply import mapply
  from .arginfo import arginfo
  from .sentinel import Sentinel, NOT_FOUND
  from .error import RegistrationError, KeyExtractorError, NoImplicitLookupError
  from .predicate import (Predicate, PredicateRegistry, KeyIndex, ClassIndex,
                          key_predicate, class_predicate,
                          match_key, match_instance, match_argname,
                          match_class)
  
new_contents: # flake8: noqa
  from .implicit import implicit
  from .registry import Registry, CachingKeyLookup, Lookup
  from .dispatch import dispatch
  from .mapply import mapply
  from .arginfo import arginfo
  from .argextract import KeyExtractor
  from .sentinel import Sentinel, NOT_FOUND
  from .error import RegistrationError, KeyExtractorError, NoImplicitLookupError
  from .predicate import (Predicate, PredicateRegistry, KeyIndex, ClassIndex,
                          key_predicate, class_predicate,
                          match_key, match_instance, match_argname,
                          match_class)
  
subject: Add KeyExtractor to exports.