PVFoamReader is not defined when using pvpython with openfoam result

Hello

I am trying to make automated post-process for particle simulation solved by OpenFOAM

First, I made test.OpenFOAM file first using
paraFoam -touch

Then, then run
pypython test.py

the message below, however, is popped up.

Traceback (most recent call last):
File “test.py”, line 33, in
ppOpenFOAM = PVFoamReader(FileName=‘test.OpenFOAM’)
NameError: name ‘PVFoamReader’ is not defined

It is wired because this function is working when I type it on python script shell in paraview.
It seems that PVFoamReader is not loaded when I use pvbatch. Could you let me know how to pre-load PVFoamReader?

I am using paraview v5.6 and latest openfoam-dev now.

Thank you in advance.