public Optional<DocumentParseInfo> parseDocument() throws IOException {
        DocumentParser documentParser = new DocumentParser(parser);
        return documentParser.parse(Optional.empty());
    }
Initialize Vespa documents/updates/removes from an InputStream containing a
valid JSON representation of a feed.

@author Steinar Knutsen
@author Haakon Dybdahl
document/src/main/java/com/yahoo/document/json/JsonReader.java