Improve TorchScript model identification logic in torch_model.py

- Updated copyright notice to reflect the years 2021-2025.
- Enhanced the logic for identifying TorchScript models by clarifying the required files and directories in the zip archive format.

Signed-off-by: Gigon Bae <gbae@nvidia.com>

Author: gigony

monai/deploy/core/models/torch_model.py

@@ -1,4 +1,4 @@
-# Copyright 2021 MONAI Consortium
+# Copyright 2021-2025 MONAI Consortium
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
@@ -24,11 +24,12 @@ class TorchScriptModel(Model):
     """Represents TorchScript model.
 
     TorchScript serialization format (TorchScript model file) is created by torch.jit.save() method and
-    the serialized model (which usually has .pt or .pth extension) is a ZIP archive containing many files.
+    the serialized model (which usually has .pt or .pth extension) is a ZIP archive.
     (https://github.com/pytorch/pytorch/blob/master/torch/csrc/jit/docs/serialization.md)
 
-    We consider that the model is a torchscript model if its unzipped archive contains files named 'data.pkl' and
-    'constants.pkl', and folders named 'code' and 'data'.
+    We identify a file as a TorchScript model if its unzipped archive contains a 'code/' directory
+    and a 'data.pkl' file. For tensor constants, it may contain either a 'constants.pkl' file (older format)
+    or a 'constants/' directory (newer format).
 
     When predictor property is accessed or the object is called (__call__), the model is loaded in `evaluation mode`
     from the serialized model file (if it is not loaded yet) and the model is ready to be used.
@@ -85,31 +86,38 @@ def train(self, mode: bool = True) -> "TorchScriptModel":
 
     @classmethod
     def accept(cls, path: str):
-        prefix_code = False
-        prefix_data = False
-        prefix_constants_pkl = False
-        prefix_data_pkl = False
+        # These are the files and directories we expect to find in a TorchScript zip archive.
+        # See: https://github.com/pytorch/pytorch/blob/main/torch/csrc/jit/docs/serialization.md
+        has_code_dir = False
+        has_constants_dir = False
+        has_constants_pkl = False
+        has_data_pkl = False
 
         if not os.path.isfile(path):
             return False, None
 
         try:
-            zip_file = ZipFile(path)
-            for data in zip_file.filelist:
-                file_name = data.filename
-                pivot = file_name.find("/")
-                if pivot != -1 and not prefix_code and file_name[pivot:].startswith("/code/"):
-                    prefix_code = True
-                if pivot != -1 and not prefix_data and file_name[pivot:].startswith("/data/"):
-                    prefix_data = True
-                if pivot != -1 and not prefix_constants_pkl and file_name[pivot:] == "/constants.pkl":
-                    prefix_constants_pkl = True
-                if pivot != -1 and not prefix_data_pkl and file_name[pivot:] == "/data.pkl":
-                    prefix_data_pkl = True
-        except BadZipFile:
+            with ZipFile(path) as zip_file:
+                # Top-level directory name in the zip file (e.g., 'model_name/')
+                top_level_dir = ""
+                if "/" in zip_file.filelist[0].filename:
+                    top_level_dir = zip_file.filelist[0].filename.split("/", 1)[0] + "/"
+
+                filenames = {f.filename for f in zip_file.filelist}
+
+                # Check for required files and directories
+                has_data_pkl = (top_level_dir + "data.pkl") in filenames
+                has_code_dir = any(f.startswith(top_level_dir + "code/") for f in filenames)
+
+                # Check for either constants.pkl (older format) or constants/ (newer format)
+                has_constants_pkl = (top_level_dir + "constants.pkl") in filenames
+                has_constants_dir = any(f.startswith(top_level_dir + "constants/") for f in filenames)
+
+        except (BadZipFile, IndexError):
             return False, None
 
-        if prefix_code and prefix_data and prefix_constants_pkl and prefix_data_pkl:
+        # A valid TorchScript model must have code/, data.pkl, and either constants.pkl or constants/
+        if has_code_dir and has_data_pkl and (has_constants_pkl or has_constants_dir):
             return True, cls.model_type
 
         return False, None