Assign a party in write off move lines without it

__init__.py

@@ -3,6 +3,7 @@
 #the full copyright notices and license terms.
 from trytond.pool import Pool
 from .account import *
+from .move import *
 
 
 def register():
@@ -10,4 +11,5 @@ def register():
         AccountTemplate,
         Account,
         Line,
+        Move,
         module='account_move_party_required', type_='model')

move.py

@@ -0,0 +1,35 @@
+#This file is part of Tryton.  The COPYRIGHT file at the top level of
+#this repository contains the full copyright notices and license terms.
+from trytond.pool import Pool, PoolMeta
+from trytond.transaction import Transaction
+
+
+__all__ = ['Move']
+__metaclass__ = PoolMeta
+
+
+class Move:
+    __name__ = 'account.move'
+
+    @classmethod
+    def create(cls, vlist):
+        pool = Pool()
+        Account = pool.get('account.account')
+        MoveLine = pool.get('account.move.line')
+        context = Transaction().context
+        if context['active_model'] == 'account.move.line':
+            party = None
+            for active_id in context['active_ids']:
+                move_line = MoveLine(active_id)
+                if getattr(move_line, 'party'):
+                    party = move_line.party
+                    break
+            if party:
+                for value in vlist:
+                    for line in value['lines']:
+                        for line_values in line[1]:
+                            account = Account(line_values['account'])
+                            if (account.party_required
+                                    and 'party' not in line_values):
+                                line_values['party'] = party
+        return super(Move, cls).create(vlist)