def set_r0_multiplier(params_dict, mul):
    """[summary]

    Args:
        params_dict (dict): model parameters
        mul (float): float to multiply lockdown_R0 by to get post_lockdown_R0

    Returns:
        dict: model parameters with a post_lockdown_R0
    """    
    new_params = params_dict.copy()
    new_params['post_lockdown_R0']= params_dict['lockdown_R0']*mul
    return new_params