orm.go
func (io IndexOptions) String() string {
	mopt := map[string]interface{}{}
	if io.keysSet {
		mopt["keys"] = io.keys
	}
	if io.trackExistenceSet {
		mopt["trackExistence"] = io.trackExistence
	}
	return fmt.Sprintf(`{"options":%s}`, encodeMap(mopt))
}
func (io IndexOptions) String() string {
	mopt := map[string]interface{}{}
	if io.keysSet {
		mopt["keys"] = io.keys
	}
	if io.trackExistenceSet {
		mopt["trackExistence"] = io.trackExistence
	}
	return fmt.Sprintf(`{"options":%s}`, encodeMap(mopt))
}
// String serializes this index to a JSON string.