I just noticed this, which is a bit troubling :
class LarkGrammarLoader(filefinder2.machinery.SourceFileLoader):
# TODO : investigate : removing get_code breaks loader !!!
[...]
Somehow it seems get_code is necessary for other methods to be found and used...
Probably should dig more into https://www.python.org/dev/peps/pep-0302/
There might be something a little different between python3 implementation and filefinder here...