in catalog/models/products.py [0:0]
def _need_variation_field(self, other, field_name)->List[str]:
# check one of two products is missing a particular variation field
if not getattr(self, field_name) and getattr(other, field_name):
return ["orig"]
elif getattr(self, field_name) and not getattr(other, field_name):
return ["new"]
return []