Creating a subprotocol with AsyncContextManager in python 3.8 works properly:

from typing_extensions import Protocol, AsyncContextManager

class Example(AsyncContextManager, Protocol):
    test: str

However in python < 3.8 (Actually only tested in Python 3.6 and 3.7) the above raises a TypeError:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.7/abc.py", line 126, in __new__
    cls = super().__new__(mcls, name, bases, namespace, **kwargs)
  File "/usr/local/lib/python3.7/typing.py", line 847, in __init_subclass__
    super().__init_subclass__(*args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/typing_extensions.py", line 1541, in __init_subclass__
    ' protocols, got %r' % base)
TypeError: Protocols can only inherit from other protocols, got <class 'contextlib.AbstractAsyncContextManager'>