func (s *Statement) Equals(other *Statement) (eq bool) {
	world_lock.Lock()
	rs := s.raptor_statement()
	ro := other.raptor_statement()
	if C.raptor_statement_equals(rs, ro) != 0 {
		eq = true
	}
	C.raptor_free_statement(rs)
	C.raptor_free_statement(ro)
	world_lock.Unlock()
	return
}
func (s *Serializer) add(statement *Statement) (err error) {
	rs := statement.raptor_statement()
	if C.raptor_serializer_serialize_statement(s.serializer, rs) != 0 {
		err = errors.New("raptor_serializer_serialize_statement failed")
	}
	C.raptor_free_statement(rs)
	return
}