def METHOD_NAME(self, rho: DNDarray) -> Union[DNDarray, float]:
    """
    Soft threshold operator
    Parameters
    ----------
    rho : DNDarray
        Input model data, Shape = (1,)
    out : DNDarray or float
        Thresholded model data, Shape = (1,)
    """
    if rho < -self.__lam:
        return rho + self.__lam
    elif rho > self.__lam:
        return rho - self.__lam
    else:
        return 0.0