update Instance.args setter

lm_eval/api/instance.py

@@ -38,6 +38,9 @@ class Instance:
         Update the arguments of this instance with a new one
         """
         if isinstance(new_arguments, tuple):
+            assert (
+                len(new_arguments) == len(self.args)
+            ), "Must set new Instance arguments to have same size + types as old arguments"
             self.arguments = new_arguments
         else:
-            print("Please enter a valid arguments tuple")
+            raise ValueError("Must set new Instance args to a tuple!")