code: def tri_filter(self, inplace=False):
          
          trifilter = vtk.vtkTriangleFilter()
          trifilter.SetInputData(self)
          trifilter.PassVertsOff()
          trifilter.PassLinesOff()
          trifilter.Update()
  
          mesh = _get_output(trifilter)
          if inplace:
              self.overwrite(mesh)
          else:
              return mesh
docs: Returns an all triangle mesh.  More complex polygons will be broken
          down into triangles.
  
          Parameters
          ----------
          inplace : bool, optional
              Updates mesh in-place while returning nothing.
  
          Returns
          -------
          mesh : vtki.PolyData
              Mesh containing only triangles.  None when inplace=True