How to use the smspdu.SMS_SUBMIT function in smspdu

def gen_tpdu(ref, to, text, empty):
    # TP-PID = 40 ==> short message type 0
    # TP-DCS = c3 ==> disable "other message indicator" and discard message
    if empty:
        text = ""
    TPPID = 0x40 if empty else 0
    TPDCS = 0xc3 if empty else 0
    pdu = SMS_SUBMIT.create(None, to, text, tp_pid=TPPID, tp_dcs=TPDCS).toPDU()
    return [pdu]

def parse(rp_message):
    rpdu = RPDU.fromPDU(rp_message)
    sms_submit = SMS_SUBMIT.fromPDU(rpdu.user_data, rpdu.rp_originator_address)
    exports = [
        ("vbts_text", sms_submit.user_data),
        ("vbts_tp_user_data", smspdu_charstring_to_hex(sms_submit.tp_ud)),
        ("vbts_tp_data_coding_scheme", sms_submit.tp_dcs),
        ("vbts_tp_protocol_id", sms_submit.tp_pid),
        ("vbts_tp_dest_address", sms_submit.tp_da),
        ("vbts_tp_dest_address_type", sms_submit.tp_toa),
        ("vbts_tp_message_type", sms_submit.tp_mti),
        ("vbts_rp_dest_address", rpdu.rp_destination_address),
        ("vbts_rp_originator_address", rpdu.rp_originator_address),
        ("vbts_rp_originator_address_type", rpdu.rp_originator_address_type),
        ("vbts_rp_message_reference", rpdu.rp_message_reference),
        ("vbts_rp_message_type", rpdu.rp_mti)
    ]
    exports = [(x, clean(y)) for (x, y) in exports]
    return exports