code: def get_issuer(request):
          
  
          elem = OneLogin_Saml2_XML.to_etree(request)
          issuer = None
          issuer_nodes = OneLogin_Saml2_XML.query(elem, '/samlp:LogoutRequest/saml:Issuer')
          if len(issuer_nodes) == 1:
              issuer = OneLogin_Saml2_XML.element_text(issuer_nodes[0])
          return issuer
docs: Gets the Issuer of the Logout Request Message
          :param request: Logout Request Message
          :type request: string|DOMDocument
          :return: The Issuer
          :rtype: string