<<< native [ EDelimited "(" ")" [ Right (EGrouped [ ESub (EIdentifier "a") (ENumber "1") , ESymbol Pun "," , ESub (EIdentifier "a") (ENumber "2") , ESymbol Pun "," , ESub (EIdentifier "a") (ENumber "3") ]) ] ] >>> tex \left( {a_{1},a_{2},a_{3}} \right)