# File lib/sass/selector/sequence.rb, line 79
      def do_extend(extends, seen = Set.new)
        paths = Haml::Util.paths(members.map do |sseq_or_op|
            next [[sseq_or_op]] unless sseq_or_op.is_a?(SimpleSequence)
            extended = sseq_or_op.do_extend(extends, seen)
            choices = extended.map {|seq| seq.members}
            choices.unshift([sseq_or_op]) unless extended.any? {|seq| seq.superselector?(sseq_or_op)}
            choices
          end)
        Haml::Util.flatten(paths.map {|path| weave(path)}, 1).map {|p| Sequence.new(p)}
      end