anchor.diff:      {error, not_supported}.
   
   probe_reset(S) ->
  -    {ok, S#st{data = []}}.
  +    {ok, S#st{data = initial_data(S#st.datapoints)}}.
   
   probe_sample(_) ->
       {error, not_supported}.
  
positive.code: 
  probe_get_value(DPs, #st{data = Data0,
                           datapoints = DPs0} = S) ->
      Data1 = if Data0 =:= undefined ->
                      [];
                 true -> Data0
              end,
      DPs1 = if DPs =:= default -> DPs0;
                true -> DPs
             end,
      {ok, probe_get_value_(Data1, DPs1), S#st{data = Data1}}.
  
  probe_get_value_(Data, DPs) ->
      [D || {K,_} = D <- Data,
  
negative.code: -include_lib("exometer_core/include/exometer.hrl").
  
  -define(DATAPOINTS, [updates]).
  -define(INITIAL_DATA, [{updates, 0}]).
  
  -record(st, {
            datapoints = ?DATAPOINTS,
            data
           }).
  
  ad_hoc_spec() ->
      [{module, ?MODULE},
       {type, probe},
       {sample_interval, infinity}].
  
  -spec behaviour() -> exometer:behaviour().
  