error with qtcharts

[teskor]

#include <QApplication>
#include <QMainWindow>
#include <QtCharts>
#include <QNetworkAccessManager>
#include <QNetworkReply>
#include <QJsonDocument>
#include <QJsonObject>
#include <QJsonArray>

using namespace QtCharts; //error here

why does it give such an error, qtcharts is connected, but nothing works

error: Expected namespace name

[Christian Ehrlicher]

See https://doc.qt.io/qt-6/qtcharts-changes-qt6.html