<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def congestionControl(Cause_presence=0):
 """CONGESTION CONTROL Section 9.3.4"""

    a = TpPd(pd=0x3)
    b = MessageType(mesType=0x39)  # 00111001
    c = CongestionLevelAndSpareHalfOctets()
    packet = a / b / c
    if Cause_presence is 1:
        e = CauseHdr(ieiC=0x08, eightBitC=0x0)
        packet = packet / e
    return packet