code: def flatten(l):
      """flatten a list of lists"""
      return [item for sublist in l for item in sublist]
  
file_path: NeMo/nemo/collections/nlp/data/text_normalization/utils.py
imports: import string
  from copy import deepcopy
  import regex
  from tqdm import tqdm
  from nemo.collections.nlp.data.text_normalization import constants
label_desc: Use image node_id 1 for calling a global function with example usage: flatten(l) and returns: unknown