code: def every_xml_doc
        every_page do |page|
          if (block_given? && page.xml?)
            if (doc = page.doc)
              yield doc
            end
          end
        end
      end
docs: Pass every XML document that the agent parses to a given block.
  
   @yield [doc]
     The block will be passed every XML document parsed.
  
   @yieldparam [Nokogiri::XML::Document] doc
     A parsed XML document.
  
   @see http://nokogiri.rubyforge.org/nokogiri/Nokogiri/XML/Document.html