. . . "40.02 (28) Employer means the state, including each state agency, any county, city, village, town, school district, other governmental unit or instrumentality of 2 or more units of government now existing or hereafter created within the state, any federated public library system established under s. 43.19 whose territory lies within a single county with a population of 500,000 or more, a local e" . .