code: def id2unit(self, id):
      if len(self.ignore) > 0 and id == EMPTY_ID:
          return "_"
      else:
          return super().id2unit(id)
  
file_path: stanza/stanza/models/pos/vocab.py
imports: from collections import Counter, OrderedDict
  from stanza.models.common.vocab import BaseVocab, BaseMultiVocab, CharVocab
  from stanza.models.common.vocab import CompositeVocab, VOCAB_PREFIX, EMPTY, EMPTY_ID
label_desc: Use image node_id 2 for calling the WordVocab obj's underlying member method code with example usage: obj.id2unit(id) and returns: str, super