anchor.diff:  %% @doc
   %% @end
   %% -----------------------------------------------------------------------------
  +-spec new() -> t().
  +
   new() ->
       state_orset:new().
   
  
positive.code: 
  -opaque t()   ::  state_orset:state_orset().
  
  -export_type[(t/0)].
  
  %% API
  -export([add/3]).
  
negative.code: %% @doc
  %% @end
  %% -----------------------------------------------------------------------------
  -spec add(node_spec(), Actor :: actor(), t()) -> t().
  
  add(#{name := _} = NodeSpec, Actor, T0) ->
      {ok, T} = state_orset:mutate({add, NodeSpec}, Actor, T0),
      T.
  