anchor.diff:      %% Wrap single value in a list for consistency
       [Value].
   
  +extract_values(Values) when is_list(Values) ->
  +    [extract_value(Value) || Value <- Values];
  +extract_values(Values) ->
  +    %% Wrap single value in a list for consistency
  +    [extract_value(Values)].
  +
  +extract_value(#{<<"value">> := Value}) ->
  +    Value;
  +extract_value(Value) ->
  +    Value.
  +
   to_labelled_list(Values) ->
       ListValues = to_list(Values),
       [#{<<"rdfs:label">> => Value} || Value <- ListValues].
  
positive.code: map(Record) ->
      Record.
  
  map_property(Key, [#{<<"value">> := Value}], Acc) ->
      %% Flatten Adlib's @lang/value xmltype=grouped structure.
      map_property(Key, Value, Acc);
  map_property(Key, #{<<"value">> := Value}, Acc) ->
      %% Flatten Adlib's @lang/value xmltype=grouped structure.
      map_property(Key, Value, Acc);
  
negative.code:     map_property/3,
      year/1,
      to_list/1,
      to_labelled_list/1,
      extract_values/1
  ]).
  
  -include_lib("zotonic.hrl").
  