typing_extensions is imported in xarray/core/npcompat.py and xarray/core/utils.py.

However, typing-extensions is not a dependency in setup.cfg, and I get the following error when I install with pip install git+https://github.com/pydata/xarray using python 3.9:

import xarray

ModuleNotFoundError: No module named 'typing_extensions'