code: def parse
        case File.extname list
        when '.xml' || '.opml'
          Nokogiri::XML(load_list).xpath('//@xmlUrl').map(&:value)
        when '.json'
          JSON.parse(load_list)
        when '.txt'
          load_list.split("\n")
        end
      end
docs: Parses OPML, JSON, or plain text documents and returns an Array of feed urls.
  
   @return [Array]