Flux Query - Top X of a tag from series

[Trolls]

Hi,

i search a way to get the top 2 (hdd_id) with the values Read_IOPS
I tried with several function without success:

from(bucket: v.bucket)
|> range(start: v.timeRangeStart, stop: v.timeRangeStop)
|> filter(fn: (r) => r._measurement == "HDD")
|> filter(fn: (r) => r.serial == "${Serial}")
|> filter(fn: (r) => r._field == "Read_IOPS")
|> aggregateWindow(every: v.windowPeriod, fn: mean)
|> highestAverage(n:2,groupColumns: ["hdd_id"])
//|> tail(n: 2)

the only result i can have is a table, not a graph.

Many thanks for any help,

Br,