def extract_bgnbd_params(model):
    """Extracts params from the (M)BG/NBD model

    Args:
        model: the (M)BG/NBD model.

    Returns:
        The a, b, r and alpha params of the (M)BG/NBD model.
    """
    r, alpha, a, b = model._unload_params('r', 'alpha', 'a', 'b')
    return {'r': r, 'alpha': alpha, 'a': a, 'b': b}