code: def hline_score(self, y, xmin, xmax):
          
          return self._hline_score[y, xmin, xmax]
docs: Returns the number of unbroken paths of qubits
  
          >>> [(x,y,0,k) for x in range(xmin,xmax+1)]
  
          for :math:`k = 0,1,\cdots,L-1`.  This is precomputed for speed.