docs: def sorted_for_ner(crf_classes):
      """
      Return labels sorted in a default order suitable for NER tasks:
  
      >>> sorted_for_ner(['B-ORG', 'B-PER', 'O', 'I-PER'])
      ['O', 'B-ORG', 'B-PER', 'I-PER']
      """
      def key(cls):
          if len(cls) > 2 and cls[1] == '-':
              # group names like B-ORG and I-ORG together
              return cls.split('-', 1)[1], cls
          return '', cls
      return sorted(crf_classes, key=key)