def add_problem_hparams(hparams, problem_name, model_dir, problem_instance):
    """Add problem hparams for the problems."""
    hparams.problems = []
    hparams.problem_instances = []
    p_hparams = problem_instance.get_hparams(hparams)
    hparams.problem_instances.append(problem_instance)
    hparams.problems.append(p_hparams)
