ruby on rails – How to create xml element with attribute with colon in Nokogiri

i am new to Ruby on Rails , I m trying to generating a xml file using Nokogiri. It is working fine as we expected but one scenario unable to generate attributes, below is the example

Expecting

<tag:tagGuideline>
    <tagClassCd>54341</tagClassCd>
    <tagClassCdDesc>test description</tagClassCdDesc>
</tag:tagGuideline> 

i did something , but it is creating differently

 <tag:tagGuideline>
    <tag:tagClassCd>54341</tag:tagClassCd>
    <tag:tagClassCdDesc>test description</tag:tagClassCdDesc>
   </tag:tagGuideline>

Here is my working code

builder = Nokogiri::XML::Builder.new do |xml|
      xml.root('xmlns:tag' => 'v1') {
       xml('tag').tagGuideline do 
        xml.ClassCd '54341'
        xml.ClassCdDesc 'test description'
       end           
      }
    end
    puts builder.to_xml

Thanks