pysnmp: How to set SysUpTimeInstance to something else than 0 when using sendNotification for sending snmp trap

I have some equipment that can send snmp traps for alarms etc. I need to simulate this equipment for testing purpose. The output from the tester must be exactly like the output from the equipment but I need to control values etc. I have created a Python script using pysnmp and sendNotification for this. It seems to work fine. However the DISMAN-EVENT-MIB::sysUpTimeInstance is send automaticaly by sendNotification and the uptime is always 0. How can I set this value to something else? I know I can put an extra object in the addVarBinds but this will just give an extra object with another value. The initial sysUpTimeInstance is still 0.
pysnmp 4.4.12
pysnmp-pyasn1 1.1.3
pysnmp-pysmi 1.1.10
pysnmplib 5.0.21

from pysnmp.hlapi import *

iterator7 = sendNotification(
    SnmpEngine(),
    CommunityData('public', mpModel=1),
    UdpTransportTarget(('localhost', 162)),
    ContextData(),
    'trap',
     NotificationType(ObjectIdentity('NET-SNMP-EXAMPLES-MIB', 'netSnmpExampleNotification')).addVarBinds(ObjectType(ObjectIdentity('NET-SNMP-EXAMPLES-MIB','netSnmpExampleHeartbeatRate'), 1))
)

errorIndication, errorStatus, errorIndex, varBinds = next(iterator7)

if errorIndication:
    print(errorIndication)

The object used in the above are just examples. I have a another MIB file with the correct objects.
The above example will result in the following received:
DISMAN-EVENT-MIB::sysUpTimeInstance = Timeticks: (0) 0:00:00.00 SNMPv2-MIB::snmpTrapOID.0 = OID: NET-SNMP-EXAMPLES-MIB::netSnmpExampleNotification NET-SNMP-EXAMPLES-MIB::netSnmpExampleHeartbeatRate = INTEGER: 1
I am receiving snmp traps with snmptrapd

If you are using pysnmp-lextudio package, the following code should work,

import asyncio
from pysnmp.hlapi.asyncio import *

async def run():
    snmpEngine = SnmpEngine()
    # Example of how you might update sysUpTime
    mibBuilder = snmpEngine.msgAndPduDsp.mibInstrumController.mibBuilder
    sysUpTime, = mibBuilder.importSymbols('__SNMPv2-MIB', 'sysUpTime')
    sysUpTime.syntax = TimeTicks(12345)  # Set uptime to 12345

    trap_result = await sendNotification(
        snmpEngine,
        CommunityData('public', mpModel=1),
        UdpTransportTarget(('localhost', 162)),
        ContextData(),
        "trap",
        NotificationType(ObjectIdentity('NET-SNMP-EXAMPLES-MIB', 'netSnmpExampleNotification')).addVarBinds(ObjectType(ObjectIdentity('NET-SNMP-EXAMPLES-MIB','netSnmpExampleHeartbeatRate'), 1))
    )
    errorIndication, errorStatus, errorIndex, varBinds = await trap_result
    if errorIndication:
        print(errorIndication)

    snmpEngine.transportDispatcher.closeDispatcher()


asyncio.run(run())

No guarantee if you are using other pysnmp packages.