<<< native [ EUnderover False (EUnderover False (EIdentifier "BASE") (EIdentifier "under-1") (EPhantom (EIdentifier "fail"))) (EIdentifier "under-2") (EPhantom (EIdentifier "fail")) , ESymbol Rel "=" , EUnder False (EUnder False (EIdentifier "BASE") (EIdentifier "under-1")) (EIdentifier "under-2") ] >>> mml $$\underset{\mathrm{under-2}}{\overset{\phantom{\mathrm{fail}}}{\underset{\mathrm{under-1}}{\overset{\phantom{\mathrm{fail}}}{\mathrm{BASE}}}}}=\underset{\mathrm{under-2}}{\underset{\mathrm{under-1}}{\mathrm{BASE}}}$$