Magento 2 – Where to find LESS Mixin definition?

In the file vendormagentotheme-frontend-lumawebcsssource_breadcrumbs.less there is this code getting called:

& when (@media-common = true) {
    .breadcrumbs {
        .lib-breadcrumbs();
    }
}

Lets say the mixin .lib-breadcrumbs() is defined multiple times in different files. How can I figure out where the mixin which is called is located? Is there a stacktrace or something which I can look into?