r - create a initial_split for multiple datasets nested on a tibble in R

Question

I´m trying to fit several models and wanted to use a tibble to organize all the data, however I´m stuck at trying to split each dataset

here is the example:

    library(tidyverse)
    library(tidymodels)

    my_data <-crossing(labels = c("A", "B", "C", "D"),
        first_var = seq(1,100, 200),
        second_var = rnorm(100, 0.25, 0.02))

    my_data_nested <- my_data %>% nest(vars = c(first_var, second_var))

  # A tibble: 4 x 2 
  labels vars              
  <chr>  <list>            
1 A      <tibble [100 x 2]>
2 B      <tibble [100 x 2]>
3 C      <tibble [100 x 2]>
4 D      <tibble [100 x 2]>

I´d like to add a column with the "initial_split" from the rsample package

when I try:

    my_data_i_split <- my_data_nested %>% map(vars  ~ initial_split(.x))
   Error: Can't convert a two-sided formula to a function
   Run `rlang::last_error()` to see where the error occurred.    

I get this error that goes well above my r knowledge.