texmath-0.13.1.2: test/roundtrip/munder-12.native

[ EUnder False (EIdentifier "B") (EIdentifier "underscript")
, ESymbol Rel "="
, EUnder
    False
    (EGrouped
       [ EPhantom (ENumber "1")
       , EIdentifier "B"
       , EPhantom (ENumber "1")
       ])
    (EIdentifier "underscript")
]