code: func (s *Secret) DeleteKey(key string) error {
  	s.Lock()
  	defer s.Unlock()
  
  	if s.data == nil {
  		return store.ErrYAMLNoMark
  	}
  	delete(s.data, key)
  	return s.encode()
  }
docs: // DeleteKey key will delete a single key from an decoded map