Merge

__init__.py

 # flake8: noqa
 import account_invoice
 import report
+import model

model/__init__.py

+# flake8: noqa
+
+import account_invoice

model/account_invoice.py

+
+from openerp import models, fields, api, _
+
+
+class account_invoice(models.Model):
+    _inherit = "account.invoice"
+
+    _order = "date_invoice desc"