Mimic the behavior of torch.clone for `Image` objects.

def clone(self) -> 'ImageBBox':
        "Mimic the behavior of torch.clone for `Image` objects."
        flow = FlowField(self.size, self.flow.flow.clone())
        return self.__class__(flow, scale=False, y_first=False, labels=self.labels, pad_idx=self.pad_idx)