toMap method
Implementation
Map<String, dynamic> toMap() {
Map<String, dynamic> cardData = {};
putIfValueNotNull("cvv", _cvv, cardData);
putIfValueNotNull("expiryYear", _expiryYear, cardData);
putIfValueNotNull("expiryMonth", _expiryMonth, cardData);
putIfValueNotNull("number", _number, cardData);
return cardData;
}