code: def identify_vertex_neighbours(self, vertex):
          
          vertex = self._permutation[vertex]
  
          lpl = self.lend[vertex-1]
          lp = lpl
  
          neighbours = []
  
          while True:
              lp = self.lptr[lp-1]
              neighbours.append(self.lst[lp-1]-1)
              if (lp == lpl):
                  break
  
          return self._deshuffle_simplices(neighbours)
docs: Find the neighbour-vertices in the triangulation for the given vertex
          (from the data structures of the triangulation)