code: func (s *Secret) SetValue(key, value string) error {
  	s.Lock()
  	defer s.Unlock()
  
  	if s.body == "" && s.data == nil {
  		s.data = make(map[string]interface{}, 1)
  	}
  	if s.data == nil {
  		return store.ErrYAMLNoMark
  	}
  	s.data[key] = value
  	return s.encode()
  }
docs: // SetValue sets a key to a given value. Will fail if an non-empty body exists