Here's a Python code snippet that implements a POWL model for a simplified Purchase-to-Pay process using pm4py. This process includes activities like 'Receive Purchase Request', 'Approve Request', 'Create Purchase Order', 'Receive Goods', 'Invoice Verification', and 'Payment'. It also includes a loop for handling multiple purchase orders and a choice between manual and automatic invoice verification.

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

# Define activities
receive_pr = Transition(label="Receive Purchase Request")
approve_pr = Transition(label="Approve Request")
create_po = Transition(label="Create Purchase Order")
receive_goods = Transition(label="Receive Goods")
invoice_verify = Transition(label="Invoice Verification")
payment = Transition(label="Payment")
skip = SilentTransition()

# Define loops and choices
loop_po = OperatorPOWL(operator=Operator.LOOP, children=[receive_pr, create_po, receive_goods])
choice_invoice = OperatorPOWL(operator=Operator.XOR, children=[invoice_verify, skip])

# Define the main POWL model
root = StrictPartialOrder(nodes=[loop_po, approve_pr, choice_invoice, payment])

# Add edges to define the partial order
root.order.add_edge(loop_po, approve_pr)
root.order.add_edge(approve_pr, choice_invoice)
root.order.add_edge(choice_invoice, payment)

# Print the POWL model
print(pm4py.visualization.powl_visualizer.apply(root))
```

This code will create a POWL model for the Purchase-to-Pay process and print a visual representation of it. The process flow is as follows:

1. Receive a purchase request (loop starts)
2. Approve the purchase request
3. Create a purchase order (loop continues)
4. Receive goods (loop continues)
5. Invoice verification (choice: either manual verification or skip if automated)
6. Payment
7. The loop ends after payment, and the process restarts if there are more purchase requests.