We don’t currently have a supported mechanism for this, but the most basic action can be achieved with:
from com.inductiveautomation.ignition.gateway.redundancy.types import ActivityLevel
from com.inductiveautomation.ignition.gateway import IgnitionGateway
redundancy_manager = IgnitionGateway.get().getRedundancyManager()
redundancy_manager.requestPeerActivityLevel(ActivityLevel.Active)
The above effectively requests the peer to become Active. There are some System tags available for discovering the current state of redundancy (that might be handy for deciding when to invoke the above).