code: def str2int(self, str_value):
      
      str_value = tf.compat.as_text(str_value)
      if self._str2int:
        return self._str2int[str_value]
  
      # No names provided, try to integerize
      failed_parse = False
      try:
        int_value = int(str_value)
      except ValueError:
        failed_parse = True
      if failed_parse or not 0 <= int_value < self._num_classes:
        raise ValueError("Invalid string class label %s" % str_value)
      return int_value
docs: Conversion class name string => integer.