docs: def get_active_for(self, user, user_agent=_MARK, ip_address=_MARK):
          """Return last known session for given user.
  
          :param user: user session
          :type user: `abilian.core.models.subjects.User`
  
          :param user_agent: *exact* user agent string to lookup, or `None` to have
          user_agent extracted from request object. If not provided at all, no
          filtering on user_agent.
          :type user_agent: string or None, or absent
  
          :param ip_address: client IP, or `None` to have ip_address extracted from
          request object (requires header 'X-Forwarded-For'). If not provided at
          all, no filtering on ip_address.
          :type ip_address: string or None, or absent
  
          :rtype: `LoginSession` or `None` if no session is found.
          """
          conditions = [LoginSession.user == user]
  
          if user_agent is not _MARK:
              if user_agent is None:
                  user_agent = request.environ.get("HTTP_USER_AGENT", "")
              conditions.append(LoginSession.user_agent == user_agent)
  
          if ip_address is not _MARK:
              if ip_address is None:
                  ip_addresses = request.headers.getlist("X-Forwarded-For")
                  ip_address = ip_addresses[0] if ip_addresses else request.remote_addr
              conditions.append(LoginSession.ip_address == ip_address)
  
          session = (
              LoginSession.query.filter(*conditions)
              .order_by(LoginSession.id.desc())
              .first()
          )
          return session