code: def get_word_chunk(word, chunk_size, chunk_start, reverse=False):
      if chunk_size < 1:
          raise ValueError("chunk size should be >= 1")
      if chunk_size > len(word):
          return None
      start = chunk_start - chunk_size if reverse else chunk_start
      end = chunk_start if reverse else chunk_start + chunk_size
      return word[start:end]
  
imports: from __future__ import unicode_literals
  from copy import deepcopy
  from snips_nlu.common.dict_utils import LimitedSizeDict
  from snips_nlu.constants import END, RES_MATCH_RANGE, START
label_desc: Use image node_id 2 for calling a global function with example usage: get_word_chunk(word, chunk_size, chunk_start, reverse) and returns: word, None