func (o *ObjectKey) keyString() string {
	if o.Lit != nil {
		return string(*o.Lit)
	}
	return o.ID.String()
}

// getLastKeypathComponent checks if the given expression is a path
// expression, and if so extracts the last dot separated component of
// the path. Otherwise it returns false.
func getLastKeypathComponent(e *Expression) (string, bool) {
	if len(e.And) > 1 ||
		len(e.And[0].Condition) > 1 ||
		e.And[0].Condition[0].Not != nil ||