[plt-scheme] What scheme module is this GUI code for?

I was looking at this code and it is almost the same as wxPython which
is a Python wrapper for a Xwindow system (I think I am saying that right
[I have yet to make a wrapper personally]). This is the best news so far
today... Maybe after getting wxPython into my head whatever module the
code below is for won't be totally new! 

                         ; Get the canvas's drawing context
                         (define dc (send canvas get-dc))
                         ; Make some pens and brushes
                         (define no-pen (make-object pen% "BLACK" 1
'transparent))
                         (define blue-brush (make-object brush% "BLUE"
'solid))
                         (define yellow-brush (make-object brush%
"YELLOW"
'solid))
                         (define/public (redraw-chart list-of-integers)
                           (send dc set-pen no-pen)
                           (send dc set-brush blue-brush)
                           (send dc draw-rectangle 0 0 100 200)  ; big
blue rectangle