§ 250. Construction. The provisions of this chapter have reference only to a city of the second class. This chapter is intended to be and shall be deemed and held in all courts and jurisdictions to be a public act of which the courts shall take judicial notice. This chapter shall be construed not as an act in derogation of the powers of the state but as one intended to aid the state in the execution of its duties, and shall be liberally construed so as to carry into effect the objects and purposes thereof.