anchor.diff:  -record(state, {mod :: atom(),
                   expects :: dict(),
                   valid = true :: boolean(),
  -                history = [] :: history(),
  +                history = [] :: history() | undefined,
                   original :: term(),
                   was_sticky :: boolean()}).
   
  
positive.code: handle_call({delete, Func, Arity}, _From, S) ->
      NewExpects = delete_expect(S#state.mod, {Func, Arity}, S#state.expects),
      {reply, ok, S#state{expects = NewExpects}};
  handle_call(history, _From, S) ->
      {reply, lists:reverse(S#state.history), S};
  handle_call(reset, _From, S) ->
  
negative.code: %%                                    Typically used to specify non-default,
  %%                                    garbage collection options.
  %%                                </dd>
  %%   <dt>`no_history'</dt> <dd>Do not store history of meck calls.
  %%                         </dd>
  %% </dl>
  -spec new(Mod:: atom() | [atom()], Options::[term()]) -> ok.
  new(Mod, Options) when is_atom(Mod), is_list(Options) ->
  