class Sass::CSS

def expand_commas(root)
  root.children.map! do |child|
    unless child.is_a?(Tree::RuleNode) && child.rule.first.include?(',')
      expand_commas(child) if child.is_a?(Tree::DirectiveNode)
      next child
    end
    child.rule.first.split(',').map do |rule|
      node = Tree::RuleNode.new([rule.strip])
      node.children = child.children
      node
    end
  end
  root.children.flatten!
end