code: def get_domain_resolver(self, domain_name, cur=None):
          
          get_cmd = "SELECT resolver FROM {} WHERE domain=? AND resolver != '' AND accepted=1 ORDER BY sequence DESC, parent_zonefile_index DESC LIMIT 1;".format(self.subdomain_table)
  
          cursor = None
          if cur is None:
              cursor = self.conn.cursor()
          else:
              cursor = cur
  
          db_query_execute(cursor, get_cmd, (domain_name,))
  
          rowdata = cursor.fetchone()
          if not rowdata:
              return None
  
          return rowdata['resolver']
docs: Get the last-knwon resolver entry for a domain name
          Returns None if not found.