code: func (cas *ContentAddressedStore) Put(data []byte) ([]byte, error) {
  	hasher := sha256.New()
  	_, err := hasher.Write(data)
  	if err != nil {
  		return nil, fmt.Errorf("ContentAddressedStore could not hash data: %v", err)
  	}
  	hash := hasher.Sum(nil)
  	cas.db.SetSync(hash, data)
  	return hash, nil
  }
docs: // These function match those used in Hoard
  // Put data in the database by saving data with a key that is its sha256 hash