How to save the image patches that are created from databunch method?

[Monk5088]

Hey author,
I was using Object detection code to create image patches using the WSI loader methods and datbunch method to wrap those images into a single fastai databunch object, but I am having issues saving those patches for reusage.
Can you please suggest how I can save the image patches I created using your code?
Here is the code that I used,

batch_size = 64

do_flip = True
flip_vert = True 
max_rotate = 90 
max_zoom = 1.1 
max_lighting = 0.2
max_warp = 0.2
p_affine = 0.75 
p_lighting = 0.75 

tfms = get_transforms(do_flip=do_flip,
                      flip_vert=flip_vert,
                      max_rotate=max_rotate,
                      max_zoom=max_zoom,
                      max_lighting=max_lighting,
                      max_warp=max_warp,
                      p_affine=p_affine,
                      p_lighting=p_lighting)
train, valid = ObjectItemListSlide(train_images) ,ObjectItemListSlide(valid_images)
item_list = ItemLists(".", train, valid)
lls = item_list.label_from_func(lambda x: x.y, label_cls=SlideObjectCategoryList)
lls = lls.transform(tfms, tfm_y=True, size=patch_size)
data = lls.databunch(bs=batch_size, collate_fn=bb_pad_collate,num_workers=0).normalize()

Now i tried saving the databunch using data.save but it throws ctype error.

The error:

ValueError                                Traceback (most recent call last)
<ipython-input-22-88cd1dd3e50b> in <module>
----> 1 data.save("test_data_bs8.pkl")

3 frames
/usr/local/lib/python3.7/dist-packages/fastai/basic_data.py in save(self, file)
    153             warn("Serializing the `DataBunch` only works when you created it using the data block API.")
    154             return
--> 155         try_save(self.label_list, self.path, file)
    156 
    157     def add_test(self, items:Iterator, label:Any=None, tfms=None, tfm_y=None)->None:

/usr/local/lib/python3.7/dist-packages/fastai/torch_core.py in try_save(state, path, file)
    414             #To avoid the warning that come from PyTorch about model not being checked
    415             warnings.simplefilter("ignore")
--> 416             torch.save(state, target)
    417     except OSError as e:
    418         raise Exception(f"{e}\n Can't write {path/file}. Pass an absolute writable pathlib obj `fname`.")

/usr/local/lib/python3.7/dist-packages/torch/serialization.py in save(obj, f, pickle_module, pickle_protocol, _use_new_zipfile_serialization)
    378         if _use_new_zipfile_serialization:
    379             with _open_zipfile_writer(opened_file) as opened_zipfile:
--> 380                 _save(obj, opened_zipfile, pickle_module, pickle_protocol)
    381                 return
    382         _legacy_save(obj, opened_file, pickle_module, pickle_protocol)

/usr/local/lib/python3.7/dist-packages/torch/serialization.py in _save(obj, zip_file, pickle_module, pickle_protocol)
    587     pickler = pickle_module.Pickler(data_buf, protocol=pickle_protocol)
    588     pickler.persistent_id = persistent_id
--> 589     pickler.dump(obj)
    590     data_value = data_buf.getvalue()
    591     zip_file.write_record('data.pkl', data_value, len(data_value))

ValueError: ctypes objects containing pointers cannot be pickled

It would be super helpful if you could look into this problem and suggest what can be done to save the image patches.
Thanks, and regards,
Harshit