code: def _serial_sanitizer(instr):
      '''Replaces the last 1/4 of a string with X's'''
      length = len(instr)
      index = int(math.floor(length * .75))
      return '{0}{1}'.format(instr[:index], 'X' * (length - index)f _serial_sanitizer(instr):
      '''Replaces the last 1/4 of a string with X's'''
      length = len(instr)
      index = int(math.floor(length * .75))
      return '{0}{1}'.format(instr[:index], 'X' * (length - index))
docs: Replaces the last 1/4 of a string with X's