fix(DRAFT): try removing Protocol altogether?

#2064 (comment)

Author: dangotbanned

narwhals/_selectors.py

@@ -10,7 +10,6 @@
 from typing import Collection
 from typing import Iterable
 from typing import Iterator
-from typing import Protocol
 from typing import Sequence
 from typing import TypeVar
 from typing import overload
@@ -23,6 +22,18 @@
 from narwhals.utils import is_compliant_dataframe
 from narwhals.utils import is_tracks_depth
 
+if not TYPE_CHECKING:
+    import sys
+
+    if sys.version_info >= (3, 9):
+        from typing import Protocol
+    else:
+        from typing import Generic
+
+        Protocol = Generic
+else:
+    from typing import Protocol
+
 if TYPE_CHECKING:
     from datetime import timezone
 

narwhals/typing.py

@@ -5,11 +5,22 @@
 from typing import Callable
 from typing import Generic
 from typing import Literal
-from typing import Protocol
 from typing import Sequence
 from typing import TypeVar
 from typing import Union
 
+if not TYPE_CHECKING:
+    import sys
+
+    if sys.version_info >= (3, 9):
+        from typing import Protocol
+    else:
+        from typing import Generic
+
+        Protocol = Generic
+else:
+    from typing import Protocol
+
 if TYPE_CHECKING:
     from types import ModuleType
     from typing import Mapping