class Sass::Selector::Sequence

def contains_parent_ref?
  members.any? do |sseq_or_op|
    next false unless sseq_or_op.is_a?(SimpleSequence)
    next true if sseq_or_op.members.first.is_a?(Parent)
    sseq_or_op.members.any? do |sel|
      sel.is_a?(Pseudo) && sel.selector && sel.selector.contains_parent_ref?
    end
  end
end