code: func (IPk *IssuerPublicKey) SetHash() error {
  	IPk.Hash = nil
  	serializedIPk, err := proto.Marshal(IPk)
  	if err != nil {
  		return errors.Wrap(err, "Failed to marshal issuer public key")
  	}
  	IPk.Hash = BigToBytes(HashModOrder(serializedIPk))
  	return nil
  }
docs: // SetHash appends a hash of a serialized public key