def raw
      r = string.present? ? string.strip : nil
      return r unless (from == "datacite" && r.present?)

      doc = Nokogiri::XML(string, nil, 'UTF-8', &:noblanks)
      node = doc.at_css("identifier")
      node.content = doi.to_s.upcase if node.present? && doi.present?
      doc.to_xml.strip
    end
def raw
      r = string.present? ? string.strip : nil
      return r unless (from == "datacite" && r.present?)

      doc = Nokogiri::XML(string, nil, 'UTF-8', &:noblanks)
      node = doc.at_css("identifier")
      node.content = doi.to_s.upcase if node.present? && doi.present?
      doc.to_xml.strip
    end
replace DOI in XML if provided in options