def base_string_uri
      Addressable::URI.parse(@attributes['uri'].to_s).tap do |uri|
        uri.scheme = uri.scheme.downcase if uri.scheme
        uri.host = uri.host.downcase if uri.host
        uri.normalize!
        uri.fragment = nil
        uri.query = nil
      end.to_s
    end
def base_string_uri
      Addressable::URI.parse(@attributes['uri'].to_s).tap do |uri|
        uri.scheme = uri.scheme.downcase if uri.scheme
        uri.host = uri.host.downcase if uri.host
        uri.normalize!
        uri.fragment = nil
        uri.query = nil
      end.to_s
    end
section 3.4.1.2

 @return [String]