docs: def _compute_suftab(self, string):
          """Computes the suffix array of a string in O(n).
  
          The code is based on that from the pysuffix library (https://code.google.com/p/pysuffix/).
  
          Kärkkäinen & Sanders (2003).
          """
          n = len(string)
          string += (unichr(1) * 3)
          suftab = np.zeros(n, dtype=np.int)
          alpha = sorted(set(string))
          self._kark_sort(string, suftab, n, alpha)
          return suftab