How to use the ipdb.exceptions.IPNotFound function in ipdb

if val > -1:
                idx = 16
                node = val

        packed = bytearray(ip.packed)
        while idx < bit_count:
            if node > self._meta.node_count:
                break
            node = self._read_node(node, (1 & (packed[idx >> 3] >> 7 - (idx % 8))))
            idx += 1
            if idx == 16 and bit_count == 128:
                self._v6offsetCache[key] = node

        if node > self._meta.node_count:
            return node
        raise IPNotFound("ip not found")