Fix bug in export using FQ ONNX in replacing activation holder with more than 8 bits with identity (#1464)

* Fix bug in export using FQ ONNX in replacing activation holder with more than 8 bits with identity

Author: lapid92

model_compression_toolkit/exporter/model_exporter/pytorch/fakely_quant_onnx_pytorch_exporter.py

@@ -78,9 +78,18 @@ def export(self, output_names=None) -> None:
             act_holder_list = [n for n, m in self.model.named_modules()
                                if isinstance(m, PytorchActivationQuantizationHolder) and
                                m.activation_holder_quantizer.num_bits > 8]
-            for act_holder in act_holder_list:  # pragma: no cover
-                delattr(self.model, act_holder)
-                setattr(self.model, act_holder, torch.nn.Identity())
+            for act_holder in act_holder_list: # pragma: no cover
+                obj = self.model
+                attrs = act_holder.split(".")
+                for a in attrs[:-1]:
+                    obj = getattr(obj, a)
+                if hasattr(obj, attrs[-1]):
+                    delattr(obj, attrs[-1])
+                    setattr(obj, attrs[-1], torch.nn.Identity())
+                else:
+                    Logger.info(f"During removal of activation quantization of a quantizer (with bits > 8) in ONNX FQ "
+                                f"export, deletion of activation holder '{act_holder}' failed — could not locate one or"
+                                f"more intermediate attributes in the path.")
 
             for layer in self.model.children():
                 self.is_layer_exportable_fn(layer)