code: def get_issuer(request):
          
          if isinstance(request, etree._Element):
              elem = request
          else:
              if isinstance(request, Document):
                  request = request.toxml()
              elem = fromstring(request, forbid_dtd=True)
  
          issuer = None
          issuer_nodes = OneLogin_Saml2_Utils.query(elem, '/samlp:LogoutRequest/saml:Issuer')
          if len(issuer_nodes) == 1:
              issuer = OneLogin_Saml2_Utils.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