I have the following data:

```
| parent_sku |    sku   | stock_status | regular_price | tax_class | 
|:----------:|:--------:|:------------:|:-------------:|:---------:|
| ABBBOA01   | ABBBOA01 | instock      | 1299          | parent    | 
| ABBBOA03   | ABBBOA03 | instock      | 1299          | parent    | 
| ABBBOA02   | ABBBOA02 | instock      | 1299          | parent    | 
| ABBBOA04   | ABBBOA04 | instock      | 1299          | parent    | 

```

I would like to mutate four variations for each `parent_sku`, `M`,`L`, `XL` and `XXL`. For example, the above data should be transformed to:

```
| parent_sku |    sku   | stock_status | regular_price | tax_class |    attribute_size   |
|:----------:|:--------:|:------------:|:-------------:|:---------:|:-------------------:|
| ABBBOA01   | ABBBOA01 | instock      | 1299          | parent    | M                   |
| ABBBOA01   | ABBBOA01 | instock      | 1299          | parent    | X                   |
| ABBBOA01   | ABBBOA01 | instock      | 1299          | parent    | XL                  |
| ABBBOA01   | ABBBOA01 | instock      | 1299          | parent    | XXL                 |
| ABBBOA03   | ABBBOA03 | instock      | 1299          | parent    | M                   |
| ABBBOA03   | ABBBOA03 | instock      | 1299          | parent    | L                   |
| ABBBOA03   | ABBBOA03 | instock      | 1299          | parent    | XL                  |
...
and so on

```

I have tried doing something like this:

```
data %>% group_by(parent_sku) %>%
  rowwise() %>% 
  mutate(attribute_size = 'M') %>%
  mutate(attribute_size = 'L') %>%
  mutate(attribute_size = 'XL') %>%
  mutate(attribute_size = 'XXL')

```

But this doesn't work.