https://github.com/python/typeshed/blob/2d3181523295181193bdb81eddab212d1ffde868/stdlib/builtins.pyi#L837 `Sequence[T]` allow `.index(T)` but is not supported by memoryview: example, this pass mypy ```python buf = memoryview(b"\x00\x01\x02\x03") print(buf.index(1)) ```