The Council may begin procedure for public improvements when all or part of the cost thereof is to be paid by benefitted real property, either on its own initiative or upon receipt of a petition. The Council shall prescribe by ordinance complete special-assessment procedure for such improvements. Without limiting the procedure which may thus be prescribed, it is hereby provided that such special-assessment procedure may (but is not hereby required to) provide for the issuance of special tax bills, warrants, or other evidences of special assessments; for the creation and operation of a revolving improvement fund; and/or for special-assessment bonds secured by special assessments on benefitted real property. Also, in accordance with Section 6-1 of this Charter, general-obligation bonds may also be secured by special assessments on benefitted real property.