Sure, suppose we have a hypothetical Purchase-to-Pay process which follows these steps:

1. Create Purchase Requisition (PR)
2. Approve Purchase Requisition
3. Create Purchase Order (PO)
4. Choose between:
   a. Receive standard goods
   b. Receive services upon proper completion
5. Approve Purchase Order
6. Process Invoice
7. Make Payment

We could model this into a POWL model using pm4py objects. Below is the Python code for such a model using pm4py:

```python
import pm4py
from pm4py.objects.powl.obj import StrictPartialOrder, OperatorPOWL, Transition, SilentTransition
from pm4py.objects.process_tree.obj import Operator

# Define the individual activities (transition with labels)
create_pr = Transition(label="Create PR")
approve_pr = Transition(label="Approve PR")
create_po = Transition(label="Create PO")
receive_goods = Transition(label="Receive Goods")
receive_services = Transition(label="Receive Services")
approve_po = Transition(label="Approve PO")
process_invoice = Transition(label="Process Invoice")
make_payment = Transition(label="Make Payment")

# Define the choice between receiving goods or services
receive_choice = OperatorPOWL(operator=Operator.XOR, children=[receive_goods, receive_services])

# Create the strict partial order for the POWL model, ensuring the correct sequence of activities
p2p_process = StrictPartialOrder(nodes=[create_pr, approve_pr, create_po, receive_choice, approve_po, process_invoice, make_payment])

# Define the ordering of the partial workflow (the control flow)
p2p_process.order.add_edge(create_pr, approve_pr)
p2p_process.order.add_edge(approve_pr, create_po)
p2p_process.order.add_edge(create_po, receive_choice)
p2p_process.order.add_edge(receive_choice, approve_po)
p2p_process.order.add_edge(approve_po, process_invoice)
p2p_process.order.add_edge(process_invoice, make_payment)

# Now the POWL model is defined and can be used further in pm4py for analysis or conformance checking
```

This script creates a sequence of transitions (activities) and makes a choice between receiving goods or services using an XOR operator. It also defines the order in which these activities must occur within the strict partial order. Please make sure that pm4py is properly installed in your Python environment before running this code, and adapt the specific activities to your actual Purchase-to-Pay process if needed.