class Less::Node::Mixin::Def

def to_sass_tree
  return if hide_in_sass
  mixin = Sass::Tree::MixinDefNode.new(name, @params.map do |v|
      v.value.flatten!
      [Sass::Script::Variable.new(v), v.value.to_sass_tree]
    end)
  rules.each {|r| mixin << r.to_sass_tree}
  mixin
end