code: func (tx Tx) ForEach(folders [][]byte, f func(Bucket, bytesp.Slice, bytesp.Slice) error) error {
  	return tx.Bucket(folders, func(b Bucket) error {
  		return errorsp.WithStacks(b.Bucket.ForEach(func(k, v []byte) error {
  			return errorsp.WithStacks(f(b, bytesp.Slice(k), bytesp.Slice(v)))
  		}))
  	})
  }
docs: // ForEach iterates over all key values of a folder.