§ 650. Initiation of proceeding. A proceeding for adoption of an alternative form of county government may be initiated by petition, or by resolution of the board of supervisors of the county; provided, however, that no such resolution shall be adopted by the board of supervisors after the initiation of such a proceeding by the filing of a petition therefor, or subsequent to ten days following the filing of an advance notice of filing such a petition, so long as the proceeding initiated by the petition or thereafter initiated pursuant to such advance notice is pending.