def switch_backends(self, FigureCanvasClass):
newCanvas = FigureCanvasClass(self.figure)<EOL>return newCanvas<EOL>
instantiate an instance of FigureCanvasClass

This is used for backend switching, eg, to instantiate a
FigureCanvasPS from a FigureCanvasGTK.  Note, deep copying is
not done, so any changes to one of the instances (eg, setting
figure size or line props), will be reflected in the other