per_device instead of per_gpu/error thrown when argument unknown (#4618)

* per_device instead of per_gpu/error thrown when argument unknown

* [docs] Restore examples.md symlink

* Correct absolute links so that symlink to the doc works correctly

* Update src/transformers/hf_argparser.py

Co-authored-by: Julien Chaumond <chaumond@gmail.com>

* Warning + reorder

* Docs

* Style

* not for squad

Co-authored-by: Julien Chaumond <chaumond@gmail.com>

src/transformers/hf_argparser.py

@@ -126,6 +126,9 @@ class HfArgumentParser(ArgumentParser):
         if return_remaining_strings:
             return (*outputs, remaining_args)
         else:
+            if remaining_args:
+                raise ValueError(f"Some specified arguments are not used by the HfArgumentParser: {remaining_args}")
+
             return (*outputs,)
 
     def parse_json_file(self, json_file: str) -> Tuple[DataClass, ...]: