how to "spin/spinto" an rectangular around its center or edge?

[znchb]

Please see the program below, I build an rectangular using polygon, and I want to make it spin around its Center point or around its Edge Line of rectangular ?
Is there anyone would like to help me?
Thank you very much!

import viz
import vizact
viz.go()
viz.clearcolor(viz.WHITE)
bg = viz.add('tut_ground.wrl')
pos = bg.getPosition()
viz.MainView.setPosition(pos[0],pos[1]+5,pos[2]-20)
A = [pos[0]-2, pos[1]+8, pos[2]+10 ]
B = [pos[0]+2, pos[1]+8, pos[2]+10 ]
C = [pos[0]+2, pos[1]+4, pos[2]+10 ]
D = [pos[0]-2, pos[1]+4, pos[2]+10 ]
viz.startlayer(viz.POLYGON)
viz.vertex(A)
viz.vertex(B)
viz.vertex(C)
viz.vertex(D)
Rectangular = viz.endlayer()
Rectangular.color(viz.RED)
#make it spin/spinto
#Rectangular.addAction(vizact.spinto(0,0,1, 180, 30))
Rectangular.addAction(vizact.spin(0,0,1, 90))
#---- How to make it spin around the Center of the rectangular ?-------
#---- or how to make it spin around the Edge Line of rectangular ? -----