"cv2.img_hash_PHash()"

I have problem to calculate the opencv-contrib "phash()"

```python
import cv2
image = cv2.imread( '/tmp/test.jpg' )
hashcode = cv2.img_hash_PHash( image )
print hashcode
```

Result -> phash-object:
````
<img_hash_PHash 0x7fbc4761d330>
````

Are there any docs?
Thanks a lot!