'Load the parent topic, if a child page.'

def load_prereq_parent_topic(self, storage, data):

    assert self.normalized_path
    if (not self.parent_slug):
        return
    parent_topic = storage.get_document(self.locale, self.parent_slug)
    if (parent_topic is None):
        data[u'needs'].append((u'document', self.parent_path, {}))
    else:
        data[u'parent_topic'] = parent_topic
