code: func (t *Collection) Write() error {
  	if t.store.readOnly {
  		return errors.New("store is read only")
  	}
  	rnl := t.rootAddRef()
  	defer t.rootDecRef(rnl)
  	return t.write(rnl.root)
  }
docs: // Writes dirty items of a collection BUT (WARNING) does NOT write new
  // root records.  Use Store.Flush() to write root records, which would
  // make these writes visible to the next file re-opening/re-loading.