code: def rounded_rectangle_region(width, height, radius):
    
    bmp = wx.Bitmap.FromRGBA(width, height) # Mask color is #000000
    dc = wx.MemoryDC(bmp)
    dc.Brush = wx.Brush((255,) * 3) # Any non-black would do
    dc.DrawRoundedRectangle(0, 0, width, height, radius)
    dc.SelectObject(wx.NullBitmap)
    bmp.SetMaskColour((0,) * 3)
    return wx.Region(bmp)
docs: Returns a rounded rectangle wx.Region