Lots of warnings when drawing multiple lines

I am using python 3.5 and mayavi 4.5.0 + vtk 7.1 (mayavi‑4.5.0+vtk71‑cp35‑cp35m‑win_amd64.whl downloaded from http://www.lfd.uci.edu/~gohlke/pythonlibs/#mayavi), and I ran into a problem.

I tried to run the draw-many-lines example given by the official documentation, but gets a lot of warnings in the vtkOutputWindow. The lines will be drawn eventually, but it is very slow because you have to wait until all warnings are printed.

How to fix this? Thanks.

The code is here:
http://docs.enthought.com/mayavi/mayavi/auto/example_plotting_many_lines.html

And the warnings looks like this:
....
Warning: In D:\Build\VTK\VTK-7.1.1\Common\DataModel\vtkPolyData.cxx, line 1023
vtkPolyData (00000150D4F16FE0): Building VTK_TRIANGLE 482 with less than three points, but VTK_TRIANGLE needs at least three points. Check the input.

Warning: In D:\Build\VTK\VTK-7.1.1\Common\DataModel\vtkPolyData.cxx, line 1023
vtkPolyData (00000150D4F16FE0): Building VTK_TRIANGLE 483 with less than three points, but VTK_TRIANGLE needs at least three points. Check the input.

Warning: In D:\Build\VTK\VTK-7.1.1\Common\DataModel\vtkPolyData.cxx, line 1023
vtkPolyData (00000150D4F16FE0): Building VTK_TRIANGLE 484 with less than three points, but VTK_TRIANGLE needs at least three points. Check the input.

Warning: In D:\Build\VTK\VTK-7.1.1\Common\DataModel\vtkPolyData.cxx, line 1023
vtkPolyData (00000150D4F16FE0): Building VTK_TRIANGLE 485 with less than three points, but VTK_TRIANGLE needs at least three points. Check the input.

Warning: In D:\Build\VTK\VTK-7.1.1\Common\DataModel\vtkPolyData.cxx, line 1023
vtkPolyData (00000150D4F16FE0): Building VTK_TRIANGLE 486 with less than three points, but VTK_TRIANGLE needs at least three points. Check the input.
....