Add improved typing for the "variant" field

[kekkox]

Hi there!👋

I made a small improvement to the code by defining a more specific type for the variant field.
By using a more specific type for the variant field, we can ensure that the code is more accurate and less prone to errors related to this field.

As this is my first contribution to an open source project, please let me know if you have any questions or concerns about the changes I've made. Thank you for considering my contribution!

Changes made:

• Defined a type that includes only the allowed values for the "variant" field