These files show examples of the three valid upAxis values and one invalid value.
upAxis = "X"
 upAxis=“X” usdrecord 22.08
upAxis=“X” usdrecord 22.08
upAxis = "Y"
 upAxis=“Y” usdrecord 22.08
upAxis=“Y” usdrecord 22.08
upAxis = "Z"
 upAxis=“Z” usdrecord 22.08
upAxis=“Z” usdrecord 22.08
upAxis = "invalid"
 upAxis=“invalid” usdrecord 22.08
upAxis=“invalid” usdrecord 22.08
#usda 1.0
(
    upAxis = "Y"
    metersPerUnit = 0.01
    defaultPrim = "World"
    subLayers = [
        @../../../_common/axis.usda@
    ]
    customLayerData = {
        string copyright = '''Copyright 2022 Apple Inc. All rights reserved.'''
    }
)