[ EDelimited
    "("
    ")"
    [ Right
        (EGrouped
           [ ESub (EIdentifier "a") (ENumber "1")
           , ESymbol Pun ","
           , ESub (EIdentifier "a") (ENumber "2")
           , ESymbol Pun ","
           , ESub (EIdentifier "a") (ENumber "3")
           ])
    ]
]