bug fix

helix/calculators/bom_helper.py

@@ -2,6 +2,7 @@ from math import ceil
 
 from helix.constants.panel_type import PanelType
 from helix.constants.parts import *
+from helix.constants.inverter_brand import InverterBrand
 
 # This story askes for this special parts to be showed 
 # www.pivotaltracker.com/n/projects/1544689/stories/148016595
@@ -41,3 +42,12 @@ def get_panel_type_counts(panels):
         panel_type_counts[panel.panel_type] += 1
 
     return panel_type_counts
+
+def is_inverter_delta(values):
+    try:
+        return (values.inverter_brands()[0]['inverter_brand_id']==InverterBrand.DELTA.value)
+    except IndexError :
+        #Some tests are calculating bom without providing inverter brand so inverter_brands is empty
+        #for those tests, inverter brand is irrelevant
+        return False
+