I wonder if it would be possible to rate the code used during the training phase. For example the code could go through various static analysis tools and the result would be assigned as metadata to the code being used to train the model. The final model would then know that a given pattern is flagged as problematic by some tool and could take this into account not just to suggest new snippets but also to suggest improvements of existing snippets. Though I suppose if it was that easy, they'd have done it already.