The right of a person to a pension, an annuity, a retirement allowance or to the return of contributions, the pension, annuity or retirement allowance itself and any optional benefit or any other right accrued or accruing to any person under this division and the moneys in the fund are hereby exempt from any state or municipal tax and exempt from levy and sale, garnishment, attachment, or any other process whatsoever and shall be unassignable except as in this division specifically otherwise provide.