class Sass::Tree::CommentNode

def normalize_indentation(str)
  pre = str.split("\n").inject(str[/^[ \t]*/].split("")) do |pre, line|
    line[/^[ \t]*/].split("").zip(pre).inject([]) do |arr, (a, b)|
      break arr if a != b
      arr + [a]
    end
  end.join
  str.gsub(/^#{pre}/, '')
end