query function adds number to operator names

[tcholewik]

When using same operator twice parser adds number to operator names.
Minimal example

>my_query <-query(list(),addToSet(list(a=1:3)))
>parse_query(my_query, pretty = TRUE)
{
  "$addToSet.a1": 1,
  "$addToSet.a2": 2,
  "$addToSet.a3": 3
} 

Expected to receive

{
  "$addToSet": {
    a: [1,2,3]
  }
}