Polygon Rubberband Python

mCanvas = iface.mapCanvas()
rb = QgsRubberBand(mCanv,True) #shouldn't this create a polygon shaped band?

rb.addPoint(QgsPoint(300,300))
rb.addPoint(QgsPoint(400,400))
rb.addPoint(QgsPoint(400,600))

print rb.asGeometry().exportToWkt()

LINESTRING(300.0 300.0, 400.0 400.0, 400.0 600.0)