PySnmp - Retrieve just a single mib tree with the bulk command?

Question

I was using the following code.

iterator = bulkCmd(
            SnmpEngine(),
            credentials,
            UdpTransportTarget((target_ip, 161), timeout=10, retries=1),
            ContextData(),
            0, 2,
            ObjectType(ObjectIdentity(oid)),
            lexicographicMode=False
        )

In the process of troubleshooting why snmpv3 randomly times out when getting polled using the above code, i was noticing that using the values (0, 100) for example, When trying to poll a simple mib for say ifAlias, i would get all the ifAlias, But also parts of the next mib. For whatever reason it seems to cause the python script to get too many timeouts. Debugging in wireshark i was seeing it (The cisco switch) was replying with more than what i was asking for leading me to believe it's taking a bit too long to reply with what i was looking for. Is there a way to get PySNMP to just pull the mib itself and anything under that tree? I feel like i'm missing something stupid in the documentation.

Thanks in advance for any pointers.