<<< native [ EUnderover False (EIdentifier "_ baseline _") (EPhantom (EIdentifier "fail")) (EPhantom (EIdentifier "fail")) , ESymbol Rel "=" , EIdentifier "_ baseline _" ] >>> mml $$\underset{\phantom{\mathrm{fail}}}{\overset{\phantom{\mathrm{fail}}}{\mathrm{\_\; baseline\; \_}}}=\mathrm{\_\; baseline\; \_}$$