module Nokogiri::XML::Searchable

def xpath_query_from_css_rule(rule, ns)
  visitor = Nokogiri::CSS::XPathVisitorOptimallyUseBuiltins.new
  self.class::IMPLIED_XPATH_CONTEXTS.map do |implied_xpath_context|
    CSS.xpath_for(rule.to_s, {:prefix => implied_xpath_context, :ns => ns,
                              :visitor => visitor})
  end.join(" | ")
end