mypy

9bbb93cf - Typeshed cherry-pick: Add __eq__ to types.MappingProxyType (#9580) (#14507)

Typeshed cherry-pick: Add __eq__ to types.MappingProxyType (#9580) (#14507) This fixes a false positive when using `--strict-equality`. See https://github.com/python/typeshed/commit/d5b88c552cd7530b598b6369fef66bda745de93d for context.