code: def read_key(fd):
      """[str] = read_key(fd)
      Read the utterance-key from the opened ark/stream descriptor 'fd'.
      """
      str_ = ""
      while True:
          char = fd.read(1)
          if char == "":
              break
          if char == " ":
              break
          str_ += char
      str_ = str_.strip()
      if str_ == "":
          return None  # end of file,
      return str_
  
imports: from __future__ import print_function
  from __future__ import division
  import argparse
  import logging
  import math
  import os
  import subprocess
  import sys
  import threading
label_desc: Use image node_id 20 for calling a global function with example usage: read_key(fd) and returns: str_, None