Google App Engineのback-referencesについて

教えてエラい人

http://code.google.com/appengine/docs/datastore/entitiesandmodels.html#Referencesの

# To fetch and iterate over every SecondModel entity that refers to the
# FirstModel instance obj1:
for obj in obj1.firstmodel_set:
  # ...

って，英文の解釈が間違って無ければ"for obj in obj1.secondmodel_set:"だと思うんだけどなぁ．．．