[docs] [issue37145] collections.abc.MappingView mixins rely on undocumented _mapping

Geoffrey Sneddon <geoffers+pythonbugs@gmail.com> added the comment: How do you use ItemsView without: * relying on __init__ and _mapping, which are both private implementation details, or * reimplementing __len__, __contains__, and __iter__? Given you can't use the mixin implementations of __len__, __contains__, and __iter__ without relying on private implementation details, should they actually be considered mixin implementations? Shouldn't they just be abstract methods given you can't actually use them? ---------- _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue37145> _______________________________________