DSL EXPRESSION:
$["abc"] = "def"


AST:
"block" [tt:block] [nt:StatementBlock]
    "=" [tt:equals] [nt:Assignment]
        "$[]" [tt:$[]] [nt:IndirectFieldValue]
            ""abc"" [tt:string_literal] [nt:string_literal]
        ""def"" [tt:string_literal] [nt:string_literal]

