code: def blit(self, bbox=None):
          
          if bbox is None:
              self.bitmap = _convert_agg_to_wx_bitmap(self.get_renderer(), None)
              self.gui_repaint()
              return
  
          l, b, w, h = bbox.bounds
          r = l + w
          t = b + h
          x = int(l)
          y = int(self.bitmap.GetHeight() - t)
  
          srcBmp = _convert_agg_to_wx_bitmap(self.get_renderer(), None)
          srcDC = wx.MemoryDC()
          srcDC.SelectObject(srcBmp)
  
          destDC = wx.MemoryDC()
          destDC.SelectObject(self.bitmap)
  
          destDC.BeginDrawing()
          destDC.Blit(x, y, int(w), int(h), srcDC, x, y)
          destDC.EndDrawing()
  
          destDC.SelectObject(wx.NullBitmap)
          srcDC.SelectObject(wx.NullBitmap)
          self.gui_repaint()
docs: Transfer the region of the agg buffer defined by bbox to the display.
          If bbox is None, the entire buffer is transferred.