code: def request(self, filter=None, stream_name=None, start_time=None, stop_time=None):
          
          node = new_ele_ns("create-subscription", NETCONF_NOTIFICATION_NS)
          if filter is not None:
              node.append(util.build_filter(filter))
          if stream_name is not None:
              sub_ele(node, "stream").text = stream_name
  
          if start_time is not None:
              sub_ele(node, "startTime").text = start_time
  
          if stop_time is not None:
              if start_time is None:
                  raise ValueError("You must provide start_time if you provide stop_time")
              sub_ele(node, "stopTime").text = stop_time
  
          return self._request(node)
docs: Creates a subscription for notifications from the server.
  
          *filter* specifies the subset of notifications to receive (by
          default all notificaitons are received)
  
          :seealso: :ref:`filter_params`
  
          *stream_name* specifies the notification stream name. The
          default is None meaning all streams.
  
          *start_time* triggers the notification replay feature to
          replay notifications from the given time. The default is None,
          meaning that this is not a replay subscription. The format is
          an RFC 3339/ISO 8601 date and time.
  
          *stop_time* indicates the end of the notifications of
          interest. This parameter must be used with *start_time*. The
          default is None, meaning that (if *start_time* is present) the
          notifications will continue until the subscription is
          terminated. The format is an RFC 3339/ISO 8601 date and time.