ParseError: Unexpected input in anonymous-file-0.less on line 31, column 8
29| 	vertical-align: middle;
30| }
31| opacity(@opacity) {
32| 	@opacity_percentage: @opacity * 100;
33|     -ms-filter: ~"progid:DXImageTransform.Microsoft.Alpha(opacity=@{opacity_percentage})"; 
34|     filter: ~"alpha(opacity = @{opacity_percentage})";