code: func (s *Store) Register(d volume.Driver, name string) bool {
  	if name == "" {
  		return false
  	}
  
  	s.mu.Lock()
  	defer s.mu.Unlock()
  
  	if _, exists := s.extensions[name]; exists {
  		return false
  	}
  
  	if err := validateDriver(d); err != nil {
  		return false
  	}
  
  	s.extensions[name] = d
  	return true
  }
docs: // Register associates the given driver to the given name, checking if
  // the name is already associated