code: def get_nameid_format(request, key=None):
          
          name_id_format = None
          name_id_data = OneLogin_Saml2_Logout_Request.get_nameid_data(request, key)
          if name_id_data and 'Format' in name_id_data.keys():
              name_id_format = name_id_data['Format']
          return name_id_format
docs: Gets the NameID Format of the Logout Request Message
          :param request: Logout Request Message
          :type request: string|DOMDocument
          :param key: The SP key
          :type key: string
          :return: Name ID Format
          :rtype: string