docs: def signed_in_users(session=None, today=None, full_name=True):
      """Return list of names of currently signed in users.
  
      :param session: SQLAlchemy session through which to access the database.
      :param today: (optional) The current date as a `datetime.date` object. Used for testing.
      :param full_name: (optional) Whether to display full user names, or just first names.
      :return: List of currently signed in users.
      """ # noqa
      if session is None:
          session = Session()
      else:
          session = session
  
      if today is None:
          today = date.today()
      else:
          today = today
  
      signed_in_users = (
          session
          .query(User)
          .filter(Entry.date == today)
          .filter(Entry.time_out.is_(None))
          .filter(User.user_id == Entry.user_id)
          .all()
      )
  
      session.close()
      return signed_in_users