The JSON is generated by running [JSON.stringify](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/stringify) on the object in page and consequent [JSON.parse](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/JSON/parse) in puppeteer. \*\*NOTE\*\* The method throws if the referenced object is not stringifiable.