Multiple training phases with different configurations

I want to do some complicated training using RLlib and I’m not sure how.

I have an environment for two agents, and I want to train the first agent while I’m forcing the policy of the second agent to be a hard-coded policy that I write. I want to run that training for 10 steps. Then I want to continue training both agents normally for 10 more steps. That means that in the second training, the first agent is starting out with the policy that I trained in the first training phase, while the second agent is starting with a blank policy.

Is that possible with RLlib? How?

Thanks for your help,
Ram Rachum.