anchor.diff:  
   %% @private
   collect_mf(Registry, Callback) ->
  -  [Callback(create_boolean(Name, Help, {Labels, Registry, DU})) ||
  -    [Name, {Labels, Help}, _, DU, _] <- prometheus_metric:metrics(?TABLE,
  +  [Callback(create_boolean(Name, Help, {Labels, Registry})) ||
  +    [Name, {Labels, Help}, _, _, _] <- prometheus_metric:metrics(?TABLE,
                                                                     Registry)],
     ok.
   
   %% @private
  -collect_metrics(Name, {Labels, Registry, DU}) ->
  +collect_metrics(Name, {Labels, Registry}) ->
     [prometheus_model_helpers:boolean_metric(
  -     lists:zip(Labels, LabelValues),
  -     prometheus_time:maybe_convert_to_du(DU, Value)) ||
  +     lists:zip(Labels, LabelValues), Value) ||
       [LabelValues, Value] <- ets:match(?TABLE, {{Registry, Name, '$1'}, '$2'})].
   
   %%====================================================================
  
positive.code: %% isn't a list.<br/>
  %% Raises `{invalid_label_name, Name, Message}' error if `Name' isn't a valid
  %% label name.<br/>
  %% Raises `{invalid_value_error, Value, MessagE}' error if `duration_unit' is
  %% unknown or doesn't match metric name.<br/>
  %% @end
  declare(Spec) ->
    prometheus_metric:insert_mf(?TABLE, ?MODULE, Spec).
  
negative.code: %% @doc Returns the value of the boolean identified by `Registry', `Name'
  %% and `LabelValues'. If there is no boolean for `LabelValues',
  %% returns `undefined'.
  %%
  %% Raises `{unknown_metric, Registry, Name}' error if boolean named `Name'
  %% can't be found in `Registry'.<br/>
  