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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def forget_canvas(canvas):
 """ Forget about the given canvas. Used by the canvas when closed. """

    cc = [c() for c in canvasses if c() is not None]
    while canvas in cc:
        cc.remove(canvas)
    canvasses[:] = [weakref.ref(c) for c in cc]