Adds S3 registration

[topepo]

Makes sure that the tunable() method for the step is seen during method dispatch on R >= 4.0. That version had the change that

S3 method lookup now by default skips the elements of the search path between the global and base environments.

Since your package is defining a method for a generic that lives in the recipes package, this extra bit of code is needed.

library(stepdwt)
#> Loading required package: recipes
#> Loading required package: dplyr
#> 
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union
#> 
#> Attaching package: 'recipes'
#> The following object is masked from 'package:stats':
#> 
#>     step
library(tune)

rec <- recipe( ~ ., data = USArrests)
dwt_trans <- rec %>%
  step_center(all_numeric()) %>%
  step_scale(all_numeric()) %>%
  step_dwt(all_numeric(), filter = tune())

tunable(dwt_trans)
#> # A tibble: 1 x 5
#>   name   call_info        source component component_id
#>   <chr>  <list>           <chr>  <chr>     <chr>       
#> 1 filter <named list [2]> recipe step_dwt  dwt_XOaCE

^{Created on 2020-09-08 by the reprex package (v0.3.0)}

[mattsq]

Awesome, thanks Max!