<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def disconnectMsToNet(Facility_presence=0, UserUser_presence=0, SsVersionIndicator_presence=0):
 """Disconnect Section 9.3.7.2"""

    a = TpPd(pd=0x3)
    b = MessageType(mesType=0x25)  # 00100101
    c = Cause()
    packet = a / b / c
    if Facility_presence is 1:
        d = FacilityHdr(ieiF=0x1C, eightBitF=0x0)
        packet = packet / d
    if UserUser_presence is 1:
        e = UserUserHdr(ieiUU=0x7E, eightBitUU=0x0)
        packet = packet / e
    if SsVersionIndicator_presence is 1:
        f = SsVersionIndicatorHdr(ieiSVI=0x7F, eightBitSVI=0x0)
        packet = packet / f
    return packet