invalid quota resource when update volume type name

When we need to update volume type name, will call:
QUOTAS.update_quota_resource(elevated, old_type_name,name)
in this function the code below:
def update_quota_resource(self, context, old_type_name, new_type_name):
for quota in ('volumes', 'gigabytes', 'snapshots'):
    old_res = "%s_%s" % (quota, old_type_name)
    new_res = "%s_%s" % (quota, new_type_name)
    db.quota_usage_update_resource(context,
                                   old_res,
                                   new_res)
    db.quota_class_update_resource(context, # it is not necessary
                                   old_res,
                                   new_res)
    db.quota_update_resource(context,
                             old_res,
                             new_res)
As everyone knows, there is no such resource named as "%s_%s" % (quota_type, volulme_type_name) in database table of quota_classes.
in table quota_classes, there are only quota default value for new project.
Unless we manually set the default quota for volume type. These values are default values, and we don't know how the user will name the volume type before we create it,So it doesn't make sense to preset a default value for a volume type in advance.

so resource named as "%s_%s" % (quota_type, volulme_type_name) only exist in table quota_usages or quotas if we set quota for specified volume type.
will not appear in table of quota_classes.

so we not need to call quota_class_update_resource when update volume type name.