Hi, you can follow these steps, but before proceeding with the code, you need to create a sequence record.

Go to Settings -> Technical -> Sequences to create the sequence record before implementing the code.

To automate sequence generation for the Purchase model, follow these steps:

1. Go to Settings -> Technical -> Automation Rules.
2. Create a new rule.
3. Set the Model to Purchase Order.
4. Set Trigger to On Creation.
5. Action: Choose Execute Python Code.

In the Python code block, use the following:

for record in records:
    record['field_name'] = env['ir.sequence'].next_by_code('purchase.order.tn')

Replace 'field_name' with the appropriate field where you want to store the sequence.