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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 get_parent(port_id):
 """Get trunk subport's parent port"""

    session = db.get_reader_session()
    res = dict()
    with session.begin():
        subport_model = trunk_models.SubPort
        trunk_model = trunk_models.Trunk
        subport = (session.query(subport_model).
                   filter(subport_model.port_id == port_id).first())
        if subport:
            trunk = (session.query(trunk_model).
                     filter(trunk_model.id == subport.trunk_id).first())
            if trunk:
                trunk_port_id = trunk.port.id
                res = get_ports(port_id=trunk_port_id, active=False)[0]
    return res