docs: def by_ip(self, ip):
          """ Find the smallest range containing the given IP.
          """
          try:
              number = inet_aton(ip)
          except Exception:
              raise IpRange.DoesNotExist
  
          try:
              return self.filter(start_ip__lte=number, end_ip__gte=number)\
                         .order_by('end_ip', '-start_ip')[0]
          except IndexError:
              raise IpRange.DoesNotExist