code: def get_user(self, nick: str) -> User:
          
          hostmask = None
          if "!" in nick:
              nick, _, hostmask = nick.partition("!")
          user = self._users.get(nick)
          if not user:
              self._users[nick] = user = User(nick, self, hostmask=hostmask)
          elif not user.hostmask:
              user.hostmask = hostmask
          return user
docs: :param nick: nick or prefix