Not working properly for variable products

I found that the plugin does not work for variable products, if you try to filter for attributes that are the same for all variations.
In my case, we tried to apply the coupon to a certain brand of products.
Did work for all single products, but not for variable products.

From my perspective the plugin did not check all attributes for variable products, so I modified the source code accordingly.

Those who are interested can see my modifications on github, I logged an issue:
https://github.com/gnagpal22/woo-attributes-coupon/issues/3

Kind regards,

Christian Toller
tethis IT e.U.