<<< native [ ESuper (EIdentifier "S") (ENumber "3") , ESymbol Rel "=" , ESuper (EIdentifier "S") (ENumber "3") , EPhantom (EFraction NormalFrac (EIdentifier "test") (EIdentifier "failed")) ] >>> mml $$S^3=S^3\phantom{\frac{\mathrm{test}}{\mathrm{failed}}}$$