I would like to give some feedback about ...

I think that may be something wrong in a assert of the software. I checked and the same code on my laptop make the right thing. I'm not sure if I have made some mistake but I think not.

From: https://checkio.org/mission/count-neighbours/solve/

HTTP_USER_AGENT:

Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:48.0) Gecko/20100101 Firefox/48.0