code: func (d *Driver) Create(id, parent string, opts *graphdriver.CreateOpts) error {
  	if opts != nil {
  		return d.create(id, parent, opts.MountLabel, true, opts.StorageOpt)
  	}
  	return d.create(id, parent, "", true, nil)
  }
docs: // Create creates a new read-only layer with the given id.