Enable ONNX export when PyTorch and TensorFlow installed in the same environment (#15625)

src/transformers/onnx/features.py

@@ -303,8 +303,16 @@ class FeaturesManager:
             The instance of the model.
 
         """
+        # If PyTorch and TensorFlow are installed in the same environment, we
+        # load an AutoModel class by default
         model_class = FeaturesManager.get_model_class_for_feature(feature)
-        return model_class.from_pretrained(model)
+        try:
+            model = model_class.from_pretrained(model)
+        # Load TensorFlow weights in an AutoModel instance if PyTorch and
+        # TensorFlow are installed in the same environment
+        except OSError:
+            model = model_class.from_pretrained(model, from_tf=True)
+        return model
 
     @staticmethod
     def check_supported_model_or_raise(