docs: def set_who(voevent, date=None, author_ivorn=None):
      """Sets the minimal 'Who' attributes:  date of authoring, AuthorIVORN.
  
      Args:
          voevent(:class:`Voevent`): Root node of a VOEvent etree.
          date(datetime.datetime): Date of authoring.
              NB Microseconds are ignored, as per the VOEvent spec.
          author_ivorn(str): Short author identifier,
              e.g. ``voevent.4pisky.org/ALARRM``.
              Note that the prefix ``ivo://`` will be prepended internally.
  
      """
      if author_ivorn is not None:
          voevent.Who.AuthorIVORN = ''.join(('ivo://', author_ivorn))
      if date is not None:
          voevent.Who.Date = date.replace(microsecond=0).isoformat()