Odoo v12
How to disable the edit button on the form? 
Found only for tree view example (create = "false") in xml file (v12)
But this code does not work for form. 

@api.model
def fields_view_get(self, view_id=None, view_type='form', toolbar=False, submenu=False):
    res = super(VerificationPurchaseOrder, self).fields_view_get(
        view_id=view_id, view_type=view_type, toolbar=toolbar, submenu=submenu)
    if view_type == 'form':
        doc = etree.XML(res['arch'])
        for node in doc.xpath("//form"):
           ++++++++++++++++++++++++++++++++++++++++++ --|
           +RIGHT HERE ->> node.set('edit', "false")+   |---- Dose not work
           ++++++++++++++++++++++++++++++++++++++++++ --|
        res['arch'] = etree.tostring(doc, encoding='unicode')
    return res

What i do wrong?

Sorry, problem solved. Code works :)