DSL EXPRESSION:
$z = {"a":"1",}


AST:
"block" [tt:block] [nt:StatementBlock]
    "=" [tt:equals] [nt:Assignment]
        "$z" [tt:field_name] [nt:DirectFieldValue]
        "{}" [tt:{}] [nt:MapLiteral]
            ":" [tt:colon] [nt:MapLiteralKeyValuePair]
                ""a"" [tt:string_literal] [nt:string_literal]
                ""1"" [tt:string_literal] [nt:string_literal]

