Custom ItemList fails to load after exporting

I have custom classes HsImage(Image), HSImageItemList(ItemList) and HsDataBunch(ImageDataBunch). HSImageItemList has two custom keyword arguments ‘dims’ and ‘chans’ that handle whether to consider data as image data (2-dimensional) or volumetric(3-dimensional), and chans that defines which channels to use in classification.

HSImageItemList is initialized like

def __init__(self, items, dims, chans=list(range(461)), **kwargs):
        super().__init__(items, **kwargs)
        self.dims = dims
        self.chans = chans

After exporting a learner that uses these, load_learner fails with TypeError: __init__() missing 1 required positional argument: 'dims'. How can I load this with same dims that it was saved with?