model_dump: Accept variable-length debug info (pytorch#57660)

Summary:
Pull Request resolved: pytorch#57660

Ignore trailing elements so we're compatible with both old and new
models.

Test Plan: Dumped and old model.  Unit test.

Reviewed By: malfet

Differential Revision: D28531391

Pulled By: dreiss

fbshipit-source-id: 197a55ab0e6a7d8e25cbee83852e194afacc988e

torch/utils/model_dump/__init__.py

@@ -246,8 +246,7 @@ def ist(s):
 
             code_parts = []
             for di, di_next in zip(debug_info, debug_info[1:]):
-                # accounting for source range serialization format change
-                start, source_range, _ = di
+                start, source_range, *_ = di
                 end = di_next[0]
                 assert end > start
                 source, s_start, s_end = source_range