Unpack Episode from episode XML element.

def _unpack_episode(element: ET.Element):
    """Unpack Episode from episode XML element."""
    return Episode(
        epno=element.find('epno').text,
        type=int(element.find('epno').get('type')),
        length=int(element.find('length').text),
        titles=tuple(_unpack_episode_title(title)
                     for title in element.iterfind('title')),
    )