Example: When a doc doesn't contain any Named Entity, the view_dictionary doesn't contain the key: NER_CONLL. I think the key should still be present, but the cons_list should be empty. In both cases, the user will need a check (check for key VS. check for empty list) and I not sure which is more standard. IMO, returning an empty list is more intuitive. What ever you think is correct. @danyaljj