[PT FE] Inherit signature from forward while patching (#27413)

### Details:
 - *Inherit signature from forward while patching*

### Tickets:
 - *ticket-id*

---------

Signed-off-by: Maxim Vafin <[email protected]>

src/bindings/python/src/openvino/frontend/pytorch/patch_model.py

@@ -4,6 +4,7 @@
 # flake8: noqa
 # mypy: ignore-errors
 
+import functools
 import logging
 import torch
 from openvino.frontend.pytorch import ModuleExtension
@@ -70,6 +71,8 @@ def new_forward(*args, **kwargs):
                     Trampoline.stashed_kwargs = kwargs
                 return extension.convert(m, Trampoline.apply, *args, **kwargs)
 
+            # make signature of new_forward same as of forward
+            new_forward = functools.wraps(m.forward)(new_forward)
             setattr(m, orig_forward_name, m.forward)
             m.forward = new_forward
 

tests/layer_tests/py_frontend_tests/test_torch_frontend.py

@@ -687,6 +687,7 @@ def test_patched_16bit_model_converts():
     from openvino.frontend.pytorch import patch_model
     from openvino import convert_model, compile_model
     import copy
+    import inspect
     from transformers.pytorch_utils import Conv1D
 
     class ModelWithLinear(torch.nn.Module):
@@ -716,6 +717,9 @@ def forward(self, x1, x2):
     model_fp16 = copy.deepcopy(model_ref).half()
 
     patch_model.__make_16bit_traceable(model_fp16)
+    # verify torch.nn.Linear signature after patching
+    signature = inspect.signature(model_ref.branch1[0].forward).parameters
+    assert ["input"] == list(signature)
     # the approach with patching only works for node with no grad
     with torch.no_grad():
         converted_model = convert_model(model_fp16, example_input=example)