'checkUnbalanced' is not defined

Hello Yade friends!

 I'm just a beginner using yade. This for sure might be a dummie question, I was wondering if someone can help me.

I'm trying to execute the example script of the oedometric test. The prompt state the following information: "name 'checkUnbalanced' is not defined". I understand that this might be because of a reading procedure from the interpreter. I used a O.step() just after the interaction loop. Nonetheless I still having the same NameError. This is the script:

$ yade-batch --job-threads=1 03-oedometric-test.table 03-oedometric-test.py
#

# load parameters from file if run in batch
# default values are used if not run from batch
readParamsFromTable(rMean=.05,rRelFuzz=.3,maxLoad=1e6,minLoad=1e4)
# make rMean, rRelFuzz, maxLoad accessible directly as variables later
from yade.params.table import *

# create box with free top, and ceate loose packing inside the box
from yade import pack, plot
O.bodies.append(geom.facetBox((.5,.5,.5),(.5,.5,.5),wallMask=31))
sp=pack.SpherePack()
sp.makeCloud((0,0,0),(1,1,1),rMean=rMean,rRelFuzz=rRelFuzz)
sp.toSimulation()

O.engines=[
   ForceResetter(),
   # sphere, facet, wall
   InsertionSortCollider([Bo1_Sphere_Aabb(),Bo1_Facet_Aabb(),Bo1_Wall_Aabb()]),
   InteractionLoop(
      # the loading plate is a wall, we need to handle sphere+sphere, sphere+facet, sphere+wall
      [Ig2_Sphere_Sphere_ScGeom(),Ig2_Facet_Sphere_ScGeom(),Ig2_Wall_Sphere_ScGeom()],
      [Ip2_FrictMat_FrictMat_FrictPhys()],
      [Law2_ScGeom_FrictPhys_CundallStrack()]
   ),
   NewtonIntegrator(gravity=(0,0,-9.81),damping=0.5),
   # the label creates an automatic variable referring to this engine
   # we use it below to change its attributes from the functions called
   PyRunner(command='checkUnbalanced()',realPeriod=2,label='checker'),
]
O.step()
O.dt=.5*PWaveTimeStep()

# the following checkUnbalanced, unloadPlate and stopUnloading functions are all called by the 'checker'
# (the last engine) one after another; this sequence defines progression of different stages of the
# simulation, as each of the functions, when the condition is satisfied, updates 'checker' to call
# the next function when it is run from within the simulation next time

# check whether the gravity deposition has already finished
# if so, add wall on the top of the packing and start the oedometric test
def checkUnbalanced():
   # at the very start, unbalanced force can be low as there is only few contacts, but it does not mean the packing is stable
   if O.iter<5000: return
   # the rest will be run only if unbalanced is < .1 (stabilized packing)
   if unbalancedForce()>.1: return
   # add plate at the position on the top of the packing
   # the maximum finds the z-coordinate of the top of the topmost particle
   O.bodies.append(wall(max([b.state.pos[2]+b.shape.radius for b in O.bodies if isinstance(b.shape,Sphere)]),axis=2,sense=-1))
   global plate # without this line, the plate variable would only exist inside this function
   plate=O.bodies[-1] # the last particles is the plate
   # Wall objects are "fixed" by default, i.e. not subject to forces
   # prescribing a velocity will therefore make it move at constant velocity (downwards)
   plate.state.vel=(0,0,-.1)
   # start plotting the data now, it was not interesting before
   O.engines=O.engines+[PyRunner(command='addPlotData()',iterPeriod=200)]
   # next time, do not call this function anymore, but the next one (unloadPlate) instead
   checker.command='unloadPlate()'

Regards and thank all of you in advance!

Aurora