code: def split_tag(chunk_tag):
      """
      split chunk tag into IOBES prefix and chunk_type
      e.g.
      B-PER -> (B, PER)
      O -> (O, None)
      """
      if chunk_tag == "O":
          return ("O", None)
      return chunk_tag.split("-", maxsplit=1)
  
file_path: graph4nlp/examples/pytorch/name_entity_recognition/conlleval.py
imports: from __future__ import division, print_function, unicode_literals
  import sys
  from collections import defaultdict
label_desc: Use image node_id 1 for calling a global function with example usage: split_tag(chunk_tag) and returns: chunk_tag, str,  None