How to write cell data changed over time into by `vtk.vtkXMLUnstructuredGridWriter`?

I have a triangle mesh, and want to write some cell data which changed over time into test.vtu files.

import numpy as np
import vtk
import vtk.util.numpy_support as vnp

mesh =vtk.vtkUnstructuredGrid()
# creat points, cellType, cells, (here we have NC cells)
mesh.SetPoints(points)
mesh.SetCells(cellType, cells)
writer = vtk.vtkXMLUnstructuredGridWriter()
writer.SetFileName("test.vtu")
writer.SetInputData(mesh)
writer.SetNumberOfTimeSteps(100)
writer.Start()

for i in range(100):
    # how to add the celldata array of current time level into mesh?
    writer.WriteNextTime(i)
writer.Stop()

But I don't know how to add the celldata array of every time level into vtk mesh. Any suggestion? Thanks very much.