“Nani” is Japanese (in Romanji form) for “what”, and in internet culture has become a common phrase of exclamation when someone is confused. It comes from the popularization of anime in American culture, but also in internet culture as a whole. In this context, it is equivalent to asking “What?” or “Huh?”. The user you replied to likely does not know what Nala is and was expressing their confusion in their comment. It’s doubtful they were replying to your comment about an apt frontend with a Python array library that hasn’t been updated in 7 years.