Apply requests from review + failing CI

Author: bigfootjon

src/graphql/pyutils/undefined.py

@@ -1,17 +1,23 @@
 """The Undefined value"""
 
 from __future__ import annotations
-from typing_extensions import Self
 
 import warnings
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    try:
+        from typing import Self
+    except ImportError:  # Python < 3.11
+        from typing_extensions import Self
 
 __all__ = ["Undefined", "UndefinedType"]
 
 
 class UndefinedType:
     """Auxiliary class for creating the Undefined singleton."""
 
-    _instance: UndefinedType | None = None
+    _instance: Self | None = None
 
     def __new__(cls) -> Self:
         """Create the Undefined singleton."""

src/graphql/type/definition.py

@@ -14,7 +14,6 @@
     cast,
     overload,
 )
-from typing_extensions import Self
 
 if TYPE_CHECKING:
     from typing import TypeAlias, TypeGuard
@@ -60,6 +59,11 @@
 if TYPE_CHECKING:
     from .schema import GraphQLSchema
 
+    try:
+        from typing import Self
+    except ImportError:  # Python < 3.11
+        from typing_extensions import Self
+
 
 __all__ = [
     "GraphQLAbstractType",