func (n Base64BigInt) MarshalJSON() ([]byte, error) {
	buf, err := ToBytes(Base64String(n))
	if err != nil {
		return nil, fmt.Errorf("could not decode base64: %v", err)
	}
	v := big.NewInt(0)
	v.SetBytes(buf)
	return []byte(v.String()), nil
}
func (n Base64BigInt) MarshalJSON() ([]byte, error) {
	buf, err := ToBytes(Base64String(n))
	if err != nil {
		return nil, fmt.Errorf("could not decode base64: %v", err)
	}
	v := big.NewInt(0)
	v.SetBytes(buf)
	return []byte(v.String()), nil
}
// MarshalJSON marshals itself.