func (s *Set) Contains(value interface{}) bool {
	s.RLock()
	defer s.RUnlock()
	_, ok := s.m[value]
	return ok
}
func (s *Set) Contains(value interface{}) bool {
	s.RLock()
	defer s.RUnlock()
	_, ok := s.m[value]
	return ok
}
// Contains check if value exists in the set.