<<< native
[ EUnderover
    False
    (EUnderover
       False
       (EIdentifier "BASE")
       (EIdentifier "under-1")
       (EIdentifier "over-2"))
    (EIdentifier "under-2")
    (EIdentifier "over-1")
, ESymbol Rel "="
, EUnderover
    False
    (EUnder
       False
       (EOver False (EIdentifier "BASE") (EIdentifier "over-2"))
       (EIdentifier "under-1"))
    (EIdentifier "under-2")
    (EIdentifier "over-1")
]
>>> tex
\underset{under-2}{\overset{over-1}{\underset{under-1}{\overset{over-2}{BASE}}}} = \underset{under-2}{\overset{over-1}{\underset{under-1}{\overset{over-2}{BASE}}}}