Add to a seq inside an ordered table

[miran]

There is also 
[mgetOrPut](https://nim-lang.github.io/Nim/tables.html#mgetOrPut,OrderedTable%5BA,B%5D,A,B),
 which you can use like this:
    
    
    for r in measuredResults:
      rates.mgetOrPut(r.rate, @[]).add(r.frequency)
    
    
    Run