§ 31. Agreement for contribution by employee void. No agreement by an employee to pay any portion of the premium paid by his employer to the state insurance fund or to contribute to a benefit fund or department maintained by such employer or to the cost of mutual insurance or other insurance, maintained for or carried for the purpose of providing compensation as herein required, shall be valid, and any employer who makes a deduction for such purpose from the wages or salary of any employee entitled to the benefits of this chapter shall be guilty of a misdemeanor.