Calculate the lowest mu

def _lowest_mu(x, fun_prediction, fun_prediction_args,
               x_bounds, x_types, minimize_constraints_fun):
    '''
    Calculate the lowest mu
    '''
    # This is only for step-wise optimization
    x = lib_data.match_val_type(x, x_bounds, x_types)

    mu = sys.maxsize
    if (minimize_constraints_fun is None) or (minimize_constraints_fun(x) is True):
        mu, _ = fun_prediction(x, *fun_prediction_args)
    return mu