Nested each don't work :(

nested-each-dont-work.scss

// File types available
    $file-types: (
        pdf: ('pdf'),
        doc: ('doc docx'),
        xls: ('xls xlsx'),
        ppt: ('ppt pptx'),
        zip: ('zip'),
        img: ('jpg jpeg gif png'),
        txt: ('txt default')
    );

    @each $type, $keys in $file-types {
        @each $key in $keys {
            #{$type} {
                font: #{$key};      // equivalent to 'content'
                content: #{$keys};
            }
        }
    }