code: func (l *LiteBackend) Imported(ctx context.Context) (imported bool, err error) {
  	err = l.inTransaction(ctx, func(tx *sql.Tx) error {
  		q, err := tx.PrepareContext(ctx,
  			"SELECT imported from meta LIMIT 1")
  		if err != nil {
  			return trace.Wrap(err)
  		}
  		row := q.QueryRowContext(ctx)
  		if err := row.Scan(&imported); err != nil {
  			if err != sql.ErrNoRows {
  				return trace.Wrap(err)
  			}
  		}
  		return nil
  	})
  	return imported, err
  }
docs: // Imported returns true if backend already imported data from another backend