Using main_dpir_sisr_real_applications.py throws AttributeError

I have duplicated `main_dpir_sisr_real_applications.py` and pointed it to my images folder. Running this script produces the following error:

```bash
k = sr.shift_pixel(k, sf)  # shift the kernel
AttributeError: module 'utils.utils_sisr' has no attribute 'shift_pixel'
```
I'm running this in CPU mode. 

Any way to fix this error or is there an updated file?

Thanks