How can I get the brands that products in this category have?

Question

Yii

Can you please tell me how can I get certain brands that products in this category have?
At the moment, I simply display all the brands like this:

$brands = Brands::find()->all();

PS:
I understand that I need a request in the form, but I don’t understand how to get the IDs of these brands!
$brands = Brands::findAll([1, 2, 3, 4]);