# File lib/sass/script/value/list.rb, line 44 def to_s(opts = {}) raise Sass::SyntaxError.new("() isn't a valid CSS value.") if value.empty? value. reject {|e| e.is_a?(Null) || e.is_a?(List) && e.value.empty?}. map {|e| e.to_s(opts)}.join(sep_str) end