[Python] Type hint for a `hashlib` `HASH' object

Consider the following MWE:

import hashlib


def tstfun(h: hashlib._hashlib.HASH):
print(h)


h = hashlib.md5()
tstfun(h)
# reveal_type(h)



Running this as-is yields - no surprise:

$ python mypytest.py
<md5 _hashlib.HASH object @ 0x7fa645dedd90>


But checking this with mypy fails with:

$ mypy mypytest.py
mypytest.py:4: error: Name 'hashlib._hashlib.HASH' is not defined
Found 1 error in 1 file (checked 1 source file)


Now, revealing the type on h (commenting in that reveal_type line):

$ mypy mypytest.py
mypytest.py:4: error: Name 'hashlib._hashlib.HASH' is not defined
mypytest.py:10: note: Revealed type is 'hashlib._Hash'
Found 1 error in 1 file (checked 1 source file)


Well, ok, then changing the type hint from hashlib._hashlib.HASH to hashlib._Hash:

$ python mypytest.py
Traceback (most recent call last):
File "/radarugs/hintze/s4-cnc-tools/mypytest.py", line 4, in <module>
def tstfun(h: hashlib._HASH):
AttributeError: module 'hashlib' has no attribute '_HASH'
$ mypy mypytest.py
mypytest.py:4: error: Name 'hashlib._HASH' is not defined
Found 1 error in 1 file (checked 1 source file)


...which is the worst outcome.

How to check if the type stubs for the hashlib are correctly found and used by mypy? What else to check? What do I get wrong?

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