relation Many2Many equipment to subscription in model equipment

equipment.py

@@ -1,5 +1,7 @@
+from collections import defaultdict
+from trytond.pool import Pool
 from trytond.model import ModelSQL, ModelView, fields
-
+from trytond.exceptions import UserError
 
 class OpticalEquipment(ModelSQL, ModelView):
     'Optical Equipment'
@@ -8,7 +10,6 @@ class OpticalEquipment(ModelSQL, ModelView):
     company = fields.Many2One('company.company', "Company")
     location = fields.Many2One('stock.location', "Location")
     party = fields.Many2One('party.party', "Party")
-    #equipment_party = fields.Many2Many('optical.equipment-party.party', 'party', 'equipment', "Equipments")
     party_address = fields.Many2One('party.address', "Party Address") 
     #origin = fields.reference("Origin", selection='get_origin', select=True)
     product = fields.Many2One('product.product', "Product")
@@ -29,15 +30,30 @@ class OpticalEquipment(ModelSQL, ModelView):
     serial = fields.Char("Serial", size=None)
     health_register = fields.Char("Health Register", size=None)
 
+    subscription_history = fields.Many2Many('sale.subscription-optical.equipment', 'equipment', 'subscription', "Subscriptions")
+    
     @staticmethod
     def get_origin():
         return None
-"""
-class OpticalEquipmentParty(ModelSQL):
-    'Optical Equipment - Party'
-    __name__ = 'optical.equipment-party.party'
-    _table = 'optical_equipment_party_party'
 
-    party = fields.Many2One('party.party', 'Party', select=True)
-    equipment = fields.Many2One('optical.equipment', 'Equipment', select=True)
-"""
+    @classmethod
+    def get_subscription_history(cls, records, names):
+        pool = Pool()
+        ids = []
+        for record in records:
+            ids.append(record.id)
+            
+        Subscriptions = pool.get('sale.subscription-optical.equipment')
+        subscriptions = Subscriptions.search([("equipment", 'in', ids)])
+        #raise UserError(str(ids))
+        subscriptions_history_id = []
+        DICC = {}
+        
+        for subscription in subscriptions:
+            DICC[subscription.equipment.id] = subscription.id
+            
+        #raise UserError(str(type(subscriptions_history_id[0])))
+        #raise UserError(str(list(subscriptions_history_id[0])))
+        #raise UserError(str(type(subscriptions_history_id)))
+
+        return DICC

subscription.py

@@ -10,5 +10,5 @@ class SubscriptionEquipment(ModelSQL):
     'Optical Equipment - Subscription'
     __name__ = 'sale.subscription-optical.equipment'
     
-    subscription = fields.Many2One('sale.subscription.line', 'Subscription Line', select=True)
+    subscription = fields.Many2One('sale.subscription', 'Subscription', select=True)
     equipment = fields.Many2One('optical.equipment', 'Equipment', select=True)

view/optical_equipment_form.xml

@@ -2,6 +2,7 @@
 <!-- This file is part of Tryton.  The COPYRIGHT file at the top level of
      this repository contains the full copyright notices and license terms. -->
 <form>
+    <field name="subscription_history"/>
     <label name="company"/>
     <field name="company"/>
     <label name="location"/>