# File soap/mimemessage.rb, line 197
  def add_part(content)
    part = Part.new
    part.headers.add("Content-Type",
      "text/xml; charset=" + XSD::Charset.encoding_label)
    part.headers.add("Content-ID", Attachment.contentid(part))
    part.body = content
    @parts.unshift(part)
  end