This function will be called after an instance is built. User input will be stored in the environment.
Examples
RAND_VAR$..init..
#> function (dist = "uniform", prm = list())
#> {
#> self$dist <- dist
#> if (!is.list(prm))
#> stop("`prm` is not a list!")
#> self$prm <- prm
#> return(invisible(self))
#> }
#> <environment: 0x10c099190>
# Instantiate
test <- rand_var(dist = "uniform", prm = list(a = 1, b = 2))
test$prm
#> $a
#> [1] 1
#>
#> $b
#> [1] 2
#>
test$dist
#> [1] "uniform"