code: def principal_chunk_width(chunk_width):
      """Given a chunk-width string like "20" or "50,70,40", returns the principal
      chunk-width which is the first element, as an int.  E.g. 20, or 40.
      """
      if not validate_chunk_width(chunk_width):
          raise Exception("Invalid chunk-width {0}".format(chunk_width))
      return int(chunk_width.split(",")[0])
  
imports: from __future__ import division
  import argparse
  import glob
  import logging
  import os
  import math
  import re
  import shutil
  import libs.common
  from libs.nnet3.train.dropout_schedule import *
  import unittest
label_desc: Use image node_id 7 for calling a global function with example usage: principal_chunk_width(chunk_width) and returns: int