def _call_power_from_driver(k, mu, theta):
    """
    Update the model and call power(k,mu) from the global driver
    instance

    This is defined at the module level so we can pickle it
    """
    from pyRSD.rsdfit import GlobalFittingDriver
    driver = GlobalFittingDriver.get()
    driver.theory.set_free_parameters(theta)
    return driver.model.power(k, mu)
