func (o *Object) GetMetadata(key string) (string, error) {
	data, ok := o.Metadata[key]
	if !ok {
		return "", fmt.Errorf("%s unexistent key", key)
	}

	return data.value, nil
}
func (o *Object) GetMetadata(key string) (string, error) {
	data, ok := o.Metadata[key]
	if !ok {
		return "", fmt.Errorf("%s unexistent key", key)
	}

	return data.value, nil
}
// SetMetadata gets a metadata value from the object.