code: def remove_empty_suppxls(suppxls):
      
      n_suppxls = np.int(suppxls.max() + 1)
      new_supps = np.zeros(suppxls.shape, dtype=np.integer)
      idx = 0
      for i in range(n_suppxls):
          sup = suppxls == i
          if sup.any():
              new_supps[np.nonzero(sup)] = idx
              idx += 1
      return new_supps
docs: Remove empty superpixels. Sometimes there are superpixels(labels), which are empty. To overcome subsequent
      problems, these empty superpixels should be removed.
      inputs:
          suppxls ... image with suppxls labels, ndarray [MxN]-same size as im
      outputs:
          new_supps ... image with suppxls labels, ndarray [MxN]-same size as im, empty superpixel labels are removed