How To get the number of author's in JSON Path version 2.2.0 ?

[Hann]

 In the older version 0.9.0 we were able to get the size of the number of authors or the count of the authors. But in the current version I am struggling to do this, I have tried to use the length() function but it does not allow me to do this . 

[kalle stenflo]

You can get the size of the book array using 

$.store.book.size()

[Hann]

Thank you very much for your answer kalle stenflo :D