this function returns all possible models with the outcome variable y, and the predictors preds.
Examples
get_all_models(c("X1", "X2"), "y", "1")
#> [[1]]
#> y ~ 1 + X1
#>
#> [[2]]
#> y ~ 1 + X2
#>
#> [[3]]
#> y ~ 1 + X1 + X2
#>
#> [[4]]
#> y ~ 1
#>