uniformize error message of init.check_keys with others

Author: ValerianRey

src/torchjd/autojac/_transform/init.py

@@ -23,5 +23,7 @@ def __call__(self, input: EmptyTensorDict) -> Gradients:
 
     def check_keys(self, input_keys: set[Tensor]) -> set[Tensor]:
         if not input_keys == set():
-            raise RequirementError(f"The input_keys should be the empty set. Found {input_keys}.")
+            raise RequirementError(
+                f"The input_keys should be the empty set. Found input_keys" f"{input_keys}."
+            )
         return self.values