Texturing a quad from within a class

[EnvisMJ]

So I'm trying to texture a quad bound to the screen from within a class.

Can anyone explain why this sample code works :

image = viz.add('Textures/VialLabels/Inventory Image - WHITE.png')
quad = viz.addTexQuad(viz.SCREEN,align=viz.TEXT_LEFT_BOTTOM,pos=(0,0,0))
quad.texture(image)
quad.setScale(6,3,1)

AND this doesn't?

import viz

class inventory(object):
	global bulkInventoryBins,medicationVials
	def __init__(self,contentsImage=""):
		self.obj = viz.add('box.wrl')
		self.obj.infoImage = contentsImage
	def showInfoImage(self):
		self.infoQuad = viz.addTexQuad(viz.SCREEN,align=viz.TEXT_LEFT_BOTTOM,pos=(0,0,0))
		self.infoQuad.texture(self.obj.infoImage)
		self.infoQuad.setScale(6,3,1)
	def removeInfoImage(self):
		self.infoQuad.remove()

A = inventory("Textures/VialLabels/Inventory Image - WHITE.png")
A.showInfoImage()
viz.go()