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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 add_current_vrf(self):
 """ Add VRF to filter list session variable """


        vrf_id = request.json['vrf_id']

        if vrf_id is not None:

            if vrf_id == 'null':
                vrf = VRF()
            else:
                vrf_id = int(vrf_id)
                vrf = VRF.get(vrf_id)

            session['current_vrfs'][vrf_id] = { 'id': vrf.id, 'rt': vrf.rt,
                    'name': vrf.name, 'description': vrf.description }
            session.save()

        return json.dumps(session.get('current_vrfs', {}))