corrections to sales

sale.py

@@ -45,8 +45,6 @@ class Sale(metaclass=PoolMeta):
         'invisible': (Eval('sale_type') != 'maintenance'),
         'readonly': True})
 
-    total_invoices = fields.Function(fields.Boolean("Invoices"), 'number_invoices')
-
     
     @classmethod
     def __setup__(cls):
@@ -93,18 +91,9 @@ class Sale(metaclass=PoolMeta):
     def get_origin_contract(cls):
         Model = Pool().get('ir.model')
         get_name = Model.get_name
-        models = cls._get_origin_contract()
+        models = cls._get_origin_contract() 
 
         return [(None, '')] + [(m, get_name(m)) for m in models]
-
-
-    @fields.depends('invoices')
-    def number_invoices(self, name):
-        number_invoices = len(self.invoices)
-        if number_invoices > 0:
-            return True
-        else:
-            return False
             
     @classmethod
     @ModelView.button
@@ -122,8 +111,6 @@ class Sale(metaclass=PoolMeta):
 
         MaintenanceService = pool.get('optical_equipment_maintenance.service')
         for sale in sales:
-            invoices = Eval('sale.invoices')
-            #raise UserError(str((invoices)))
             if sale.sale_type == 'maintenance':
                 for line in sale.lines:
                     maintenanceService = MaintenanceService(