Just for the external JSON. Other formats would probably not even be part of the datamodel module, since they do not have such a close relationship to the datamodel. The external JSON serialisation is special since it is the main interchange format for the web API (and maybe for dumps in the future). So this package would really contain just the code for this one format, not even for other JSON formats. Some of the conversion code (like for times) might be useful for other tasks as well, but we can always rename/redocument the package if it turns out to be slightly different in scope.