OAM 11.1.2 : how to modify webgate Primary Servers list using WLST

I'm following https://docs.oracle.com/cd/E52734_01/core/ASHIA/oamam.htm#ASHIA6889  doc to scale out OAM.

In addition  to standard operations (create machine, managed server, etc) there are a few OAM specific stepos

1) 6.4.17.1 Registering the Managed Server with OAM (To register the new managed server as an OAM server)

2) 6.4.17.2 Configuring WebGate with the New OAM Access Server

I'd like to perform them using WLST.

For first step I found 'createOAMServer' command but I can't find a way to perform second step. There are commands editWebgateAgent, editWebgate11gAgent but it looks like they can't manage Primary Server list parameter