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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 attachRequest(PTmsiSignature_presence=0, GprsTimer_presence=0, TmsiStatus_presence=0):
 """ATTACH REQUEST Section 9.4.1"""

    a = TpPd(pd=0x3)
    b = MessageType(mesType=0x1)  # 0000001
    c = MsNetworkCapability()
    d = AttachTypeAndCiphKeySeqNr()
    f = DrxParameter()
    g = MobileId()
    h = RoutingAreaIdentification()
    i = MsRadioAccessCapability()
    packet = a / b / c / d / f / g / h / i
    if PTmsiSignature_presence is 1:
        j = PTmsiSignature(ieiPTS=0x19)
        packet = packet / j
    if GprsTimer_presence is 1:
        k = GprsTimer(ieiGT=0x17)
        packet = packet / k
    if TmsiStatus_presence is 1:
        l = TmsiStatus(ieiTS=0x9)
        packet = packet / l
    return packet