Looking at the code (https://github.com/mozilla/bugbug/blob/master/bugbug/model.py#L184 https://github.com/mozilla/bugbug/blob/master/bugbug/model.p...), they t

Looking at the code (https://github.com/mozilla/bugbug/blob/master/bugbug/model.py#L184 https://github.com/mozilla/bugbug/blob/master/bugbug/model.p...), they test for any significant words in the code, comment, commit message, tags, etc. I wouldn't be surprised if language is explicitly included as, for example, a flag in the "data" object. But the model should be able to figure it out by itself otherwise by identifying keywords that only some languages (often) use.