code: def geodesic(self, start_vertex, end_vertex, inplace=False):
          
          if start_vertex < 0 or end_vertex > self.n_points - 1:
              raise IndexError('Invalid indices.')
  
          dijkstra = vtk.vtkDijkstraGraphGeodesicPath()
          dijkstra.SetInputData(self)
          dijkstra.SetStartVertex(start_vertex)
          dijkstra.SetEndVertex(end_vertex)
          dijkstra.Update()
  
          output = _get_output(dijkstra)
  
          if inplace:
              self.overwrite(output)
          else:
              return output
docs: Calculates the geodesic path betweeen two vertices using Dijkstra's
          algorithm.
  
          Parameters
          ----------
          start_vertex : int
              Vertex index indicating the start point of the geodesic segment.
  
          end_vertex : int
              Vertex index indicating the end point of the geodesic segment.
  
          Returns
          -------
          output : vtki.PolyData
              PolyData object consisting of the line segment between the two given
              vertices.