Add typing-extensions to dependencies

doc/getting-started-guide/installing.rst

@@ -8,6 +8,7 @@ Required dependencies
 
 - Python (3.7 or later)
 - setuptools (40.4 or later)
+- typing-extensions
 - `numpy <http://www.numpy.org/>`__ (1.17 or later)
 - `pandas <http://pandas.pydata.org/>`__ (1.0 or later)
 

setup.cfg

@@ -78,6 +78,7 @@ install_requires =
     numpy >= 1.17
     pandas >= 1.0
     setuptools >= 40.4  # For pkg_resources
+    typing-extensions  # Backported type hints
 
 [options.extras_require]
 io =

xarray/core/utils.py

@@ -6,6 +6,7 @@
 import itertools
 import os
 import re
+import sys
 import warnings
 from enum import Enum
 from typing import (
@@ -30,7 +31,12 @@
 
 import numpy as np
 import pandas as pd
-from typing_extensions import TypeGuard
+
+if sys.version_info >= (3, 10):
+    from typing import TypeGuard
+else:
+    from typing_extensions import TypeGuard
+
 
 K = TypeVar("K")
 V = TypeVar("V")