fix: typeguard import

Author: msto

fgpyo/util/metric.py

@@ -117,6 +117,7 @@
 """
 
 import dataclasses
+import sys
 from abc import ABC
 from enum import Enum
 from inspect import isclass
@@ -127,9 +128,13 @@
 from typing import Generic
 from typing import Iterator
 from typing import List
-from typing import TypeGuard
 from typing import TypeVar
 
+if sys.version_info >= (3, 10):
+    from typing import TypeGuard
+else:
+    from typing_extensions import TypeGuard
+
 import attr
 
 from fgpyo import io