func SimpleHashFromHashers(items []Hasher) []byte {
	hashes := make([][]byte, len(items))
	for i, item := range items {
		hash := item.Hash()
		hashes[i] = hash
	}
	return simpleHashFromHashes(hashes)
}
func SimpleHashFromHashers(items []Hasher) []byte {
	hashes := make([][]byte, len(items))
	for i, item := range items {
		hash := item.Hash()
		hashes[i] = hash
	}
	return simpleHashFromHashes(hashes)
}
// SimpleHashFromHashers computes a Merkle tree from items that can be hashed.