anchor.diff:  ?FORWARD1(escalus_users, delete_users).
   ?FORWARD2(escalus_users, delete_users).
   
  +?FORWARD1(escalus_users, get_users).
  +
   ?FORWARD1(escalus_story, make_everyone_friends).
   ?FORWARD3(escalus_story, story).
   
  
positive.code:          create_users/2,
           delete_users/1,
           delete_users/2,
           override/3,
           make_everyone_friends/1,
           story/3,
  
negative.code:             ok;
          {error, {already_started, _}} ->
              ok
      end.
  