Modifying the 'CSS' file in "react-search-refiners" webpart

I deployed below react-search-refiners webpart from the link.

https://github.com/SharePoint/sp-dev-solutions/tree/master/solutions/ModernSearch/react-search-refiners

But when i try to change the any CSS files "SearchBoxWebPart.module.css" example if i change the below code

 to

After i execute the "gulp serve" command it coming back to below one

So please tell me how to do the changes for this.