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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 import_dashboards(self):
 """Overrides the dashboards using json instances from the file."""

        f = request.files.get('file')
        if request.method == 'POST' and f:
            dashboard_import_export.import_dashboards(db.session, f.stream)
            return redirect('/dashboard/list/')
        return self.render_template('superset/import_dashboards.html')