This doesn't seem to work:

```py
from typing import NewType

MyStr = NewType("MyStr", str)
x = MyStr("Hello World")

isinstance(x, MyStr)

```

I don't even get `False`, but `TypeError: isinstance() arg 2 must be a type or tuple of types` because `MyStr` is a function and `isinstance` wants one or more `type`.

Even `assert type(x) == MyStr` or `is MyStr` fails.

What am I doing wrong?