Parsing issue "expected string_qt"

[jmigual]

Given the example data on the documentation:

{
    "store": {
        "book": [
            {
                "category": "reference",
                "author": "Nigel Rees",
                "title": "Sayings of the Century",
                "price": 8.95
            },
            {
                "category": "fiction",
                "author": "Evelyn Waugh",
                "title": "Sword of Honour",
                "price": 12.99
            },
            {
                "category": "fiction",
                "author": "Herman Melville",
                "title": "Moby Dick",
                "isbn": "0-553-21311-3",
                "price": 8.99
            },
            {
                "category": "fiction",
                "author": "J. R. R. Tolkien",
                "title": "The Lord of the Rings",
                "isbn": "0-395-19395-8",
                "price": 22.99
            }
        ],
        "bicycle": {
            "color": "red",
            "price": 19.95
        }
    }
}

I try the following queries:

• $..book[?(@.isbn)]: This works as given in the (https://docs.rs/jsonpath-rust/latest/jsonpath_rust/)[documentation]
• $..[?(@.isbn)]: This doesn't work but is accepted in https://jsonpath.com/. It should recursively return any object that has an isbn, not only the ones that are part of a book property.