code: def _is_dns_subdomain(name):
      ''' Check that name is DNS subdomain: One or more lowercase rfc1035/rfc1123
      labels separated by '.' with a maximum length of 253 characters '''
  
      dns_subdomain = re.compile(r)
      if dns_subdomain.match(name):
          log.debug("Name: %s is valid DNS subdomain", name)
          return True
      else:
          log.debug("Name: %s is not valid DNS subdomain", name)
          return False
docs: Check that name is DNS subdomain: One or more lowercase rfc1035/rfc1123
      labels separated by '.' with a maximum length of 253 characters