model-conversion : add warn about transformers mismatch (#18691)

This commit adds a check comparing the installed transformers library
with the transformers version that the original model supports. This
check will be performed upon a model verification failure and prints a
warning/hint to the user suggesting to install the correct version of
the transformers library.

The motivation for this change is that it is possible for the model
verification to fail due to differences in the transformers library used
and it might not be obvious that this could be the cause of the failure.
With this warning the correct version can be checked and hopefully save
time troubleshooting the cause of the verification failure.

examples/model-conversion/scripts/utils/common.py

@@ -3,6 +3,9 @@
 import os
 import sys
 import torch
+import transformers
+import json
+import textwrap
 import numpy as np
 from pathlib import Path
 
@@ -243,3 +246,54 @@ def compare_tokens(original, converted, type_suffix="", output_dir="data"):
         print(f"  ... and {len(mismatches) - num_to_show} more mismatches")
 
     return False
+
+
+def show_version_warning(current_version, model_version):
+    if not model_version:
+        return False
+
+    try:
+        from packaging.version import parse, InvalidVersion
+        try:
+            return parse(current_version) < parse(model_version)
+        except InvalidVersion:
+            return current_version != model_version
+    except ImportError:
+        return current_version != model_version
+
+def get_model_transformers_version(model_path):
+    if not model_path:
+        return None
+
+    config_path = Path(model_path) / "config.json"
+    if not config_path.is_file():
+        return None
+
+    try:
+        with open(config_path, "r", encoding="utf-8") as f:
+            config = json.load(f)
+        return config.get("transformers_version")
+    except (IOError, json.JSONDecodeError) as e:
+        print(f"Warning: Could not read or parse {config_path}: {e}", file=sys.stderr)
+        return None
+
+def exit_with_warning(message, model_path):
+    print(message)
+
+    if model_path and transformers is not None:
+        model_transformers_version = get_model_transformers_version(model_path)
+        transformers_version       = transformers.__version__
+        if show_version_warning(transformers_version, model_transformers_version):
+            warning_message = f"""
+                =====================================================================
+                Verification failure might be due to a transformers version mismatch:
+
+                Current transformers version: {transformers_version}
+                Model's required version    : {model_transformers_version}
+
+                Consider installing the version specified by the model's config:
+                pip install transformers=={model_transformers_version}
+                =====================================================================
+            """
+            print(textwrap.dedent(warning_message))
+    sys.exit(1)