anchor.diff:  process_map() ->
       gen_server:call(?MODULE, get_process_map, infinity).
   
  +contract() ->
  +    gen_server:call(?MODULE, contract, infinity).
  +
   %%%===================================================================
   %%% gen_server callbacks
   %%%===================================================================
  
positive.code: maybe_unnecessary(G, V) ->
      digraph:in_degree(G, V) =:= 1.
  
  %%%===================================================================
  %%% .DOT export functions
  %%%===================================================================
  
negative.code:          terminate/2,
           code_change/3]).
  
  %% @todo Remove. Debug only
  -export([contract/0]).
  
  %% Defines how often an optimization pass happens.
  %% A value of 0 means the optimization happens every time.
  -define(CONTRACTION_INTERVAL, 0).
  