func NewLocalClient(root string) (Client, error) {
	if err := os.MkdirAll(root, 0755); err != nil {
		return nil, err
	}
	return &localClient{root}, nil
}
func NewLocalClient(root string) (Client, error) {
	if err := os.MkdirAll(root, 0755); err != nil {
		return nil, err
	}
	return &localClient{root}, nil
}
// NewLocalClient returns a Client that stores data on the local file system