code: def clear_marking(self):
          
          if self.marktag:
              try:
                  self.canvas.delete_object_by_tag(self.marktag, redraw=False)
              except Exception:
                  pass
  
          if self.markhltag:
              try:
                  self.canvas.delete_object_by_tag(self.markhltag, redraw=False)
              except Exception:
                  pass
  
          self.treeview.clear()  # Clear table too
          self.w.nshown.set_text('0')
          self.fitsimage.redraw()
docs: Clear marking from image.
          This does not clear loaded coordinates from memory.