[Feature] Add a model_dump() function

[allenanie]

Even though model.load("checkpoint.pkl") can already produce a runnable model, sometimes, there is a need to submit a runnable Python agent to an external evaluation service (such as various competitions that evaluate the solution with hidden test inputs).

Feature request: add agent.model_dump("agent.py") or a similarly named API that allows people to create a Python file with the final learned parameters.