anchor.diff:                 metadata := Mdata,
                  resolution := Resolution} <- R2],
       R4 = [#{name => Name,
  -            metadata => Mdata,
  +            metadata => maps:map(fun to_null/2, Mdata),
               values => [#{timestamp => Ts, event => E}
                          || {Ts, E} <- Data],
               type => <<"events">>}
  
positive.code:         _ ->
              D
      end.
  
  content_type(Req) ->
      {ok, A, Req1} = cowboy_req:parse_header(<<"accept">>, Req),
  
negative.code:     R3 = [#{name => Name,
              resolution => Resolution,
              values => mmath_bin:to_list(Data),
              metadata => maps:map(fun to_null/2, Mdata),
              type => <<"metrics">>}
            || #{name := Name,
                 data := Data,
  