code: def identify_segments(self):
          
  
          lst  = self.lst
          lend = self.lend
          lptr = self.lptr
  
          segments_array = np.empty((len(lptr),2),dtype=np.int)
          segments_array[:,0] = lst[:] - 1
          segments_array[:,1] = lst[lptr[:]-1] - 1
  
          valid = np.where(segments_array[:,0] < segments_array[:,1])[0]
          segments = segments_array[valid,:]
  
          return self._deshuffle_simplices(segments)
docs: Find all the segments in the triangulation and return an
          array of vertices (n1,n2) where n1 < n2