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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def welcome(self):
 """Personalized welcome page"""

        if not g.user or not g.user.get_id():
            return redirect(appbuilder.get_url_for_login)

        welcome_dashboard_id = (
            db.session
            .query(UserAttribute.welcome_dashboard_id)
            .filter_by(user_id=g.user.get_id())
            .scalar()
        )
        if welcome_dashboard_id:
            return self.dashboard(str(welcome_dashboard_id))

        payload = {
            'user': bootstrap_user_data(),
            'common': self.common_bootsrap_payload(),
        }

        return self.render_template(
            'superset/basic.html',
            entry='welcome',
            title='Superset',
            bootstrap_data=json.dumps(payload, default=utils.json_iso_dttm_ser),
        )