User matgrioni rightfully pointed out that the default fields in the library are not the real CoNLL-U fields. They
should be in all caps, and for xpostag it should be XPOS and for upostag UPOS. Additionally, the user asked for more
control over these fields. This release accommodates that request.
- **[formatter]** Breaking change: `CONLL_FIELD_NAMES` now is in line with the CoNLL-U descriptor field names:
"ID", "FORM", "LEMMA", "UPOS", "XPOS", "FEATS", "HEAD", "DEPREL", "DEPS", "MISC". These are the new default fields.
- **[formatter]** New parameter: `field_names` that allows you to override the fields that were described above.
Simply add a dictionary of `{"default field name": "new field name"}`, e.g. `{"UPOS": "upostag"}