simple TkInter question - labels

[headspin]

I know how to switch a label from text to an image; simply config the
image property to an existing image.

But how do you do the opposite? Once a label displays an image, how do
you switch it back to displaying text? Setting the image property to
None doesn't seem to do the trick.

By the way, I initially tried to write my (very simple) app with
wxPython, but couldn't deal with the documentation.