Creating offsets to do Swarm functionality in Dronekit via Python

I am trying to create a python script that runs in DroneKit to mimic the functionality of Swarm in Mission Planner so the UAVs can maintain formation and offsets even if they lose connection to ground control. My plan is to send the mission waypoint file to the leader, then send an adjusted mission waypoint file to each of the followers that would keep the planes in a V formation. How do you set and keep the offsets in Mission Planner?