document fake TypeVar

Author: maxfischer2781

asyncstdlib/_lrucache.py

@@ -120,7 +120,7 @@ def cache_discard(self, *args: Any, **kwargs: Any) -> None:
 # these are fake and only exist for placeholders
 S = TypeVar("S")
 S2 = TypeVar("S2")
-P = TypeVar("P")
+P = TypeVar("P")  # actually a ParamSpec, see .pyi
 R = TypeVar("R")