code: def is_bio_scheme(all_tags):
      """
      Check if BIO tagging scheme is used. Return True if so.
  
      Args:
          all_tags: a list of NER tags
  
      Returns:
          True if the tagging scheme is BIO, otherwise False
      """
      for tag in all_tags:
          if tag in EMPTY_OR_O_TAG:
              continue
          elif len(tag) > 2 and tag[:2] in ("B-", "I-", "B_", "I_"):
              continue
          else:
              return False
      return True
  
file_path: stanza/stanza/models/ner/utils.py
imports: import logging
  from stanza.models.common.vocab import EMPTY
label_desc: Use image node_id 2 for calling a global function with example usage: is_bio_scheme(all_tags) and returns: True, False