Failed to run the bgp_peer example.

[chris3will]

I'm using my virtual machine, ubutnu20 LTS and player15.

I just download the z3, z3solver, and using my python 2.7 for the 2018's version.

then I download the requirements for synet-plus and the token.

when I run the bgp_peers, the things mostly seemed run well, but after printing the "Constraints adding time : xxxxx
Start Z3 check xxxx
Z3 check time: xxx
Setting the Var: xxx
Reading model time:xxxx
"

then it comes the error:
Traceback (most recent call last):
File "bgp_peers.py", line 212, in
bgp_example(args.outdir)
File "bgp_peers.py", line 203, in bgp_example
netcomplete.synthesize()
File "/home/chris/Downloads/synet-plus-master/synet/netcomplete.py", line 362, in synthesize
self.synthesize_bgp()
File "/home/chris/Downloads/synet-plus-master/synet/netcomplete.py", line 184, in synthesize_bgp
self.bgp_synthesizer.update_network_graph()
File "/home/chris/Downloads/synet-plus-master/synet/synthesis/new_propagation.py", line 435, in update_network_graph
self.ibgp_propagation.node[node]['box'].update_network_graph()
File "/home/chris/Downloads/synet-plus-master/synet/synthesis/new_bgp.py", line 607, in update_network_graph
rmap = smt_rmap.get_config()
File "/home/chris/Downloads/synet-plus-master/synet/utils/fnfree_policy.py", line 1670, in get_config
lines.append(line.get_config())
File "/home/chris/Downloads/synet-plus-master/synet/utils/fnfree_policy.py", line 1572, in get_config
actions = self.smt_actions.get_config()
File "/home/chris/Downloads/synet-plus-master/synet/utils/fnfree_policy.py", line 1448, in get_config
config = _gather_communities(communities, index)
File "/home/chris/Downloads/synet-plus-master/synet/utils/fnfree_policy.py", line 1430, in _gather_communities
assert isinstance(prev_action, ActionSetCommunity), "Found: {}".format(self.actions)
AssertionError: Found: [SetPermitted(EMPTY?Value), SetActions([SetNextHop(EMPTY?V(p(p((((((py(p(p(p((((("

so i don't know what to do , and if there is something caused by the new version nowadays 2020?
thanks for your idea! plz