code: def coarse_tag_str(pos_seq):
      """Convert POS sequence to our coarse system, formatted as a string."""
      global tag2coarse
      tags = [tag2coarse.get(tag, "O") for tag in pos_seq]
      return "".join(tags)
  
imports: from __future__ import print_function
  import os
  import re
  import sys
  from collections import Counter
label_desc: Use image node_id 2 for calling a global function with example usage: coarse_tag_str(pos_seq) and returns: str