force predicted values to None or empty base on doc type

cope2n-api/fwd_api/celery_worker/process_result_tasks.py

@@ -210,13 +210,20 @@ def _update_subscription_rq_file(request_id, index_in_request, doc_type, result)
                 purchase_date = elem['value']
             else:
                 imei_number = elem['value']
-
-    _predict_result = {
-        "retailername": retailer_name, 
-        "sold_to_party": sold_to_party, 
-        "purchase_date": purchase_date, 
-        "imei_number": imei_number 
-        }
+    if doc_type=='invoice':
+        _predict_result = {
+            "retailername": retailer_name, 
+            "sold_to_party": sold_to_party, 
+            "purchase_date": purchase_date, 
+            "imei_number": [] 
+            }
+    else:
+        _predict_result = {
+            "retailername": None, 
+            "sold_to_party": None, 
+            "purchase_date": [], 
+            "imei_number": imei_number 
+            }
     image.predict_result = _predict_result
     image.save()