code: func NewHashFromStr(hash string) (*Hash, error) {
  	ret := new(Hash)
  	err := Decode(ret, hash)
  	if err != nil {
  		return nil, err
  	}
  	return ret, nil
  }
docs: // NewHashFromStr creates a Hash from a hash string.  The string should be
  // the hexadecimal string of a byte-reversed hash, but any missing characters
  // result in zero padding at the end of the Hash.