code: def sentences_bipadding(sent):
      return "SENTENCESTART " + sent + " SENTENCEEND"
  
file_path: BigDL/python/dllib/src/bigdl/dllib/feature/dataset/sentence.py
imports: import nltk
  import os
  import itertools
  import sys
  from nltk.tokenize import word_tokenize
label_desc: Use image node_id 3 for calling a global function with example usage: sentences_bipadding(sent) and returns: unknown