how do I use r data.table env option?

I'm trying to use data.table's recommended method of programming on data.table: https://rdatatable.gitlab.io/data.table/library/data.table/doc/datatable-programming.html#get
But I just get an error.

I'm using R version 4.2.3 and data.table version 1.14.8

> packageVersion("data.table")
[1] ‘1.14.8’
> DT = as.data.table(iris)
> v1 = "Petal.Width"
> v2 = "Sepal.Width"
> DT[, .(total = sum(v1, v2)),
+    env = list(v1 = v1, v2 = v2)]
Error in `[.data.table`(DT, , .(total = sum(v1, v2)), env = list(v1 = v1,  : 
  unused argument (env = list(v1 = v1, v2 = v2))

The issue is because env is not an argument in data.table yet