Restoring one line I don't think I should have changed

Author: tleonhardt

cmd2/argparse_custom.py

@@ -319,7 +319,7 @@ def __call__(self) -> list[str]: ...  # pragma: no cover
 class ChoicesProviderFuncWithTokens(Protocol):
     """Function that returns a list of choices in support of tab completion and accepts a dictionary of prior arguments."""
 
-    def __call__(self, *, arg_tokens: dict[str, list[str]]) -> list[str]: ...  # pragma: no cover
+    def __call__(self, *, arg_tokens: dict[str, list[str]] = {}) -> list[str]: ...  # pragma: no cover  # noqa: B006
 
 
 ChoicesProviderFunc = Union[ChoicesProviderFuncBase, ChoicesProviderFuncWithTokens]