You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: signed_info_builder.rb
    path of file: ./repos/saml_idp/lib/saml_idp
    
    the code of the file until where you have to start completion: require 'builder'
module SamlIdp
  class SignedInfoBuilder
    include Algorithmable

    SIGNATURE_METHODS = {
      "sha1" => "http://www.w3.org/2000/09/xmldsig#rsa-sha1",
      "sha224" => "http://www.w3.org/2001/04/xmldsig-more#rsa-sha224",
      "sha256" => "http://www.w3.org/2001/04/xmldsig-more#rsa-sha256",
      "sha384" => "http://www.w3.org/2001/04/xmldsig-more#rsa-sha384",
      "sha512" => "http://www.w3.org/2001/04/xmldsig-more#rsa-sha512",
    }
    DIGEST_METHODS = {
      "sha1" => "http://www.w3.org/2000/09/xmldsig#sha1",
      "sha224" => "http://www.w3.org/2001/04/xmldsig-more#sha224",
      "sha256" => "http://www.w3.org/2001/04/xmlenc#sha256",
      "sha384" => "http://www.w3.org/2
    
    def raw
      builder = Builder::XmlMarkup.new
      builder.tag! "ds:SignedInfo", "xmlns:ds" => "http://www.w3.org/2000/09/xmldsig#" do |signed_info|
        signed_info.tag!("ds:CanonicalizationMethod", Algorithm: "http://www.w3.org/2001/10/xml-exc-c14n#") {}
        signed_info.tag!("ds:SignatureMethod", Algorithm: signature_method ) {}
        signed_info.tag! "ds:Reference", URI: reference_string do |reference|
          reference.tag! "ds:Transforms" do |transforms|
            transforms.tag!("ds:Transform", Algorithm: "http://www.w3.org/2000/09/xmldsig#enveloped-signature") {}
            transforms.tag!("ds:Transform", Algorithm: "http://www.w3.org/2001/10/xml-exc-c14n#") {}
          end
          reference.tag!("ds:DigestMethod", Algorithm: digest_method) {}
          reference.tag! "ds:DigestValue", digest_value
        end
      end
    end