/// <summary>
/// Obtains an access and refresh tokens by refresh token
/// </summary>
/// <returns><see cref=NdRefreshTokenResponse> instance.</returns>
public NdRefreshTokenResponse ObtainTokensByRefreshToken()
{
var refreshToken = clientData.GetSavedRefreshToken(clientData.GetClientId());
var tokens = oAuth.ObtainTokensByRefreshToken(refreshToken,
clientData.GetClientId(),
clientData.GetClientSecret(clientData.GetClientId()))
.ToResultOrException();
clientData.SaveTokens(tokens, clientData.GetClientId());
return(tokens);
}