docs: def _mlperf_print(key, value=None, benchmark=None, stack_offset=0,
                    tag_set=None, deferred=False, root_dir=None,
                    extra_print=False, prefix=""):
    ''' Prints out an MLPerf Log Line.
  
    key: The MLPerf log key such as 'CLOCK' or 'QUALITY'. See the list of log keys in the spec.
    value: The value which contains no newlines.
    benchmark: The short code for the benchmark being run, see the MLPerf log spec.
    stack_offset: Increase the value to go deeper into the stack to find the callsite. For example, if this
                  is being called by a wraper/helper you may want to set stack_offset=1 to use the callsite
                  of the wraper/helper itself.
    tag_set: The set of tags in which key must belong.
    deferred: The value is not presently known. In that case, a unique ID will
              be assigned as the value of this call and will be returned. The
              caller can then include said unique ID when the value is known
              later.
    root_dir: Directory prefix which will be trimmed when reporting calling file
              for compliance logging.
    extra_print: Print a blank line before logging to clear any text in the line.
    prefix: String with which to prefix the log message. Useful for
            differentiating raw lines if stitching will be required.
  
    Example output:
      :::MLP-1537375353 MINGO[17] (eval.py:42) QUALITY: 43.7
    '''
  
    return_value = None
  
    if (tag_set is None and not PATTERN.match(key)) or key not in tag_set:
      raise ValueError('Invalid key for MLPerf print: ' + str(key))
  
    if value is not None and deferred:
      raise ValueError("deferred is set to True, but a value was provided")
  
    if deferred:
      return_value = str(uuid.uuid4())
      value = "DEFERRED: {}".format(return_value)
  
    if value is None:
      tag = key
    else:
      str_json = json.dumps(value)
      tag = '{key}: {value}'.format(key=key, value=str_json)
  
    callsite = get_caller(2 + stack_offset, root_dir=root_dir)
    now = time.time()
  
    message = '{prefix}:::MLPv0.5.0 {benchmark} {secs:.9f} ({callsite}) {tag}'.format(
        prefix=prefix, secs=now, benchmark=benchmark, callsite=callsite, tag=tag)
  
    if extra_print:
      print() # There could be prior text on a line
  
    if tag in STDOUT_TAG_SET:
      LOGGER.info(message)
    else:
      LOGGER.debug(message)
  
    return return_value