def setupVarianceFilter():
    rgba_aovs = mc.ls(type='aiAOV')
    rgba_aovs = [aov for aov in rgba_aovs if mc.getAttr(aov + '.name') == 'RGBA']
    if not rgba_aovs:
        return
    for aov in rgba_aovs:
        drivers = mc.listConnections(aov + '.outputs[0].driver')
        if not drivers:
            continue
        filters = mc.listConnections(aov + '.outputs[0].filter')
        if not filters:
            continue

        aiAOVFilter = mc.createNode('aiAOVFilter')
        mc.setAttr(aiAOVFilter + '.aiTranslator', 'variance', type='string' )
        mc.setAttr(aiAOVFilter + '.width', mc.getAttr(filters[0] + '.width') )

        mc.connectAttr( (drivers[0] + '.message'), (aov + '.outputs[1].driver') )
        mc.connectAttr( (aiAOVFilter + '.message'), (aov + '.outputs[1].filter') )