anchor.diff:  -type instr()      :: term().
   -type transition() :: {concuerror_lid:lid(), instr(), list()}.
   -type clock_map()  :: dict(). %% dict(concuerror_lid:lid(), clock_vector()).
  -%% -type clock_vector() :: dict(). %% dict(concuerror_lid:lid(), s_i()).
  +%% -type clock_vector() :: orddict(). %% dict(concuerror_lid:lid(), s_i()).
   
   select_one_shallow_except_with_fix(DeepList, Exceptions) ->
       select_one_shallow_except_with_fix(DeepList, Exceptions, []).
  
positive.code: 
  max_cv(D1, D2) ->
      Merger = fun(_Key, V1, V2) -> max(V1, V2) end,
      dict:merge(Merger, D1, D2).
  
  check_pollable(TraceTop) ->
      #trace_state{pollable = Pollable} = TraceTop,
  
negative.code: new_lid_trace() ->
      queue:in({init_tr(), empty_clock_vector()}, queue:new()).
  
  empty_clock_vector() -> orddict:new().
  
  -type trace_state() :: #trace_state{}.
  
  