Sure, here's an example Python code to implement a hypothetical Purchase-to-Pay process tree in pm4py:

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

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

# Create the nodes for the Purchase-to-Pay process
purchase_order = ProcessTree(label="Purchase Order", parent=root)
goods_receipt = ProcessTree(label="Goods Receipt", parent=root)
invoice_receipt = ProcessTree(label="Invoice Receipt", parent=root)
three_way_match = ProcessTree(label="Three-way Match", parent=root)
pay_supplier = ProcessTree(label="Pay Supplier", parent=root)

# Create the sequence node for Goods Receipt and Invoice Receipt
goods_invoice_seq = ProcessTree(operator=Operator.SEQUENCE, parent=root)
goods_invoice_seq.children.append(goods_receipt)
goods_invoice_seq.children.append(invoice_receipt)

# Create the parallel node for Three-way Match and Pay Supplier
parallel = ProcessTree(operator=Operator.PARALLEL, parent=root)
three_way_match_node = ProcessTree(label="Three-way Match", parent=parallel)
pay_supplier_node = ProcessTree(label="Pay Supplier", parent=parallel)
parallel.children.append(three_way_match_node)
parallel.children.append(pay_supplier_node)

# Add the children to the root node
root.children.append(purchase_order)
root.children.append(goods_invoice_seq)
root.children.append(parallel)
```

This code creates a process tree for a Purchase-to-Pay process. The process starts with a Purchase Order, followed by a sequence of Goods Receipt and Invoice Receipt. After that, there's a parallel execution of Three-way Match and Pay Supplier.