Notwithstanding any provision of law requiring uniform property tax rates on real or personal property within the county, any county in this state, except a metropolitan county as defined in section 473.121, subdivision 4, and any other county containing a city of the first class, may establish subordinate service districts to provide and finance any governmental service or function which it is otherwise authorized to undertake. A function or service to be provided shall not include a function or service which the county generally provides throughout the county unless an increase in the level of the service is to be supplied in the service district.