code: func (bk *Backend) GetKeys(bucket []string) ([]string, error) {
  	// Get all the key/value pairs for this bucket.
  	items, err := bk.GetItems(bucket)
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  
  	// Return only the keys, the keys are already sorted by GetItems.
  	keys := make([]string, len(items))
  	for i, e := range items {
  		keys[i] = e.Key
  	}
  
  	return keys, nil
  }
docs: // GetKeys returns a list of keys for a given bucket.