pt-to-tf model architecture override (#22055)

* Add an argument to pt-to-tf to allow overriding the model class

* make fixup

* Minor fix to error message

* Remove unused extra conversion from the script

src/transformers/commands/pt_to_tf.py

@@ -68,6 +68,7 @@ def convert_command_factory(args: Namespace):
         args.no_pr,
         args.push,
         args.extra_commit_description,
+        args.override_model_class,
     )
 
 
@@ -126,6 +127,13 @@ class PTtoTFCommand(BaseTransformersCLICommand):
             default="",
             help="Optional additional commit description to use when opening a PR (e.g. to tag the owner).",
         )
+        train_parser.add_argument(
+            "--override-model-class",
+            type=str,
+            default=None,
+            help="If you think you know better than the auto-detector, you can specify the model class here. "
+            "Can be either an AutoModel class or a specific model class like BertForSequenceClassification.",
+        )
         train_parser.set_defaults(func=convert_command_factory)
 
     @staticmethod
@@ -175,6 +183,7 @@ class PTtoTFCommand(BaseTransformersCLICommand):
         no_pr: bool,
         push: bool,
         extra_commit_description: str,
+        override_model_class: str,
         *args,
     ):
         self._logger = logging.get_logger("transformers-cli/pt_to_tf")
@@ -185,6 +194,7 @@ class PTtoTFCommand(BaseTransformersCLICommand):
         self._no_pr = no_pr
         self._push = push
         self._extra_commit_description = extra_commit_description
+        self._override_model_class = override_model_class
 
     def get_inputs(self, pt_model, config):
         """
@@ -269,7 +279,20 @@ class PTtoTFCommand(BaseTransformersCLICommand):
         # Load config and get the appropriate architecture -- the latter is needed to convert the head's weights
         config = AutoConfig.from_pretrained(self._local_dir)
         architectures = config.architectures
-        if architectures is None:  # No architecture defined -- use auto classes
+        if self._override_model_class is not None:
+            if self._override_model_class.startswith("TF"):
+                architectures = [self._override_model_class[2:]]
+            else:
+                architectures = [self._override_model_class]
+            try:
+                pt_class = getattr(import_module("transformers"), architectures[0])
+            except AttributeError:
+                raise ValueError(f"Model class {self._override_model_class} not found in transformers.")
+            try:
+                tf_class = getattr(import_module("transformers"), "TF" + architectures[0])
+            except AttributeError:
+                raise ValueError(f"TF model class TF{self._override_model_class} not found in transformers.")
+        elif architectures is None:  # No architecture defined -- use auto classes
             pt_class = getattr(import_module("transformers"), "AutoModel")
             tf_class = getattr(import_module("transformers"), "TFAutoModel")
             self._logger.warning("No detected architecture, using AutoModel/TFAutoModel")
@@ -287,7 +310,6 @@ class PTtoTFCommand(BaseTransformersCLICommand):
         pt_model = pt_class.from_pretrained(self._local_dir)
         pt_model.eval()
 
-        tf_from_pt_model = tf_class.from_pretrained(self._local_dir, from_pt=True)
         pt_input, tf_input = self.get_inputs(pt_model, config)
 
         with torch.no_grad():