The mayor, before entering upon the duties of his or her office, shall take and subscribe the following oath or affirmation:
I do solemnly swear (affirm) that I will support the constitution of the United States and the constitution of the state of Illinois and ordinances of the city of Princeton, and that I will faithfully discharge the duties of the office of mayor of the city of Princeton, Illinois, to the best of my ability.
which oath or affirmation, so subscribed, shall be filed in the office of the city clerk.