code: def add_server(self, name, prefer=False):
          
          if not name or re.match(r'^[\s]+$', name):
              raise ValueError('ntp server name must be specified')
          if prefer:
              name = '%s prefer' % name
          cmd = self.command_builder('ntp server', value=name)
          return self.configure(cmd)
docs: Add or update an NTP server entry to the node config
  
          Args:
              name (string): The IP address or FQDN of the NTP server.
              prefer (bool): Sets the NTP server entry as preferred if True.
  
          Returns:
              True if the operation succeeds, otherwise False.