Creating a process tree for a hypothetical Purchase-to-Pay (P2P) process using the pm4py library in Python involves starting with identifying the activities that typically occur within that process and how they are ordered or related. A typical P2P process may include activities such as creating a purchase order, receiving goods, receiving an invoice, and finally, paying the invoice.

For simplicity, we'll create a simplified version of such a process with the following steps:
1. Create a purchase order (PO).
2. Then, there is a choice between receiving goods first or receiving an invoice first.
3. Once both goods and invoice are received, they are checked (in true concurrency).
4. Finally, after the check, the payment is made.

This sequence of activities can then be translated into a PM4Py process tree using the defined operators (->, X, +, *).

Here's how we can build this process tree in Python using the PM4Py library:

```python
from pm4py.objects.process_tree.obj import ProcessTree, Operator

# Create the root of the tree
root = ProcessTree(operator=Operator.SEQUENCE)

# First activity: Create a PO
create_po = ProcessTree(label="Create PO", parent=root)

# Exclusive choice between "Receive Goods" and "Receive Invoice"
receive_choice = ProcessTree(operator=Operator.XOR, parent=root)

# Option 1: Receive Goods first
receive_goods = ProcessTree(label="Receive Goods", parent=receive_choice)

# Option 2: Receive Invoice first
receive_invoice = ProcessTree(label="Receive Invoice", parent=receive_choice)

# Once both received, they are checked in true concurrency
check_concurrency = ProcessTree(operator=Operator.PARALLEL, parent=root)
check_goods = ProcessTree(label="Check Goods", parent=check_concurrency)
check_invoice = ProcessTree(label="Check Invoice", parent=check_concurrency)

# Finally, the payment is made
make_payment = ProcessTree(label="Make Payment", parent=root)

# Add children to their respective parents
root.children.extend([create_po, receive_choice, check_concurrency, make_payment])
receive_choice.children.extend([receive_goods, receive_invoice])
check_concurrency.children.extend([check_goods, check_invoice])

# At this point, the process tree has been constructed.
# You may serialize it to a different format or analyze it using PM4Py
```

The above code creates the process tree by first defining the overall sequence of events. It introduces a decision point where there's an exclusive choice (XOR) between two paths: receiving goods or receiving an invoice. Both pathways lead to a point where goods and invoice are checked in true parallelism (+), and finally, it concludes with the payment.

Always remember that since we are creating a hypothetical process tree without full knowledge of the exact activities or decisions involved in a real Purchase-to-Pay process, the structure and complexity of the actual process can vary significantly and may require additional operators or activities to be accurately modeled.