class Sass::Tree::MixinNode

def to_src(tabs, opts, fmt)
  args = '(' + @args.map {|a| a.to_sass(opts)}.join(", ") + ')' unless @args.empty?
  "#{'  ' * tabs}#{fmt == :sass ? '+' : '@include '}#{dasherize(@name, opts)}#{args}#{semi fmt}\n"
end