anchor.diff:                                  learner:start_paxosid(GLLearner, PaxId, Maj,
                                                         comm:this(), ItemId),
                                   %% add learner to running paxos acceptors
  -                                _ = [ case unknown =/= X of
  -                                          true -> comm:send(X,
  -                                                            {acceptor_add_learner,
  -                                                             PaxId, GLLearner});
  -                                          false -> ok
  -                                      end || X <- Accs],
  +                                _ = [ comm:send(X,
  +                                                {acceptor_add_learner,
  +                                                 PaxId, GLLearner})
  +                                      || X <- ValidAccs],
                                   Proposer =
                                       comm:make_global(get_my(Role, proposer)),
                                   proposer:start_paxosid(
  -                                  Proposer, PaxId, _Acceptors = Accs, abort,
  -                                  Maj, length(Accs) + 1, ThisRTMsNumber),
  +                                  Proposer, PaxId, _Acceptors = ValidAccs, abort,
  +                                  Maj, length(ValidAccs) + 1, ThisRTMsNumber),
                                   ok
                               end
                               || {PaxId, _RTLog, _TP}
  
positive.code: -type rtm() :: {?RT:key(),
                  comm:mypid() | unknown,
                  Role :: non_neg_integer(),
                  Acceptor :: comm:mypid() | unknown}.
  
  -type rtms() :: [rtm()].
  
  
negative.code:             Maj = config:read(quorum_factor),
              RTMs = tx_state:get_rtms(TxState),
              Role = state_get_role(State),
              ValidAccs = [ X || X <- rtms_get_accpids(RTMs), unknown =/= X],
              {_, _, ThisRTMsNumber, _} = lists:keyfind(comm:this(), 2, RTMs),
  
              %% add ourselves as learner and
  