def speaker_durations(utterances: List[Utterance]) -> List[Tuple[str, int]]:
    """ Takes a list of utterances and itemizes them by speaker, returning a
    list of tuples of the form (Speaker Name, duration).
    """

    speaker_utters = make_speaker_utters(utterances)

    speaker_duration_tuples = [] # type: List[Tuple[str, int]]
    for speaker in speaker_utters:
        speaker_duration_tuples.append((speaker, total_duration(speaker_utters[speaker])))

    return speaker_duration_tuples
Takes a list of utterances and itemizes them by speaker, returning a
    list of tuples of the form (Speaker Name, duration).