- This routine creates a Tk() top-level widget and iconifies it.
It is designed to work around a bug in Pmw.Blt.Graph which results in an
error if Tk() is called more than once in a Python session. Using this
routine all "top-level" Tk widgets are actually children of this hidden
If there is no Tk() top level widget (i.e. Tkinter._default_root is None)
then this routine creates a hidden Tk().
This routine always returns a Toplevel() widget that is a child of the