toJson method
Implementation
Map<String, dynamic> toJson() => {
if (transactionType != null) 'transactionType': transactionType,
if (currency != null) 'currency': currency,
if (amount != null) 'amount': amount,
if (decimals != null) 'decimals': decimals,
if (fromAddress != null) 'fromAddress': fromAddress,
if (toAddress != null) 'toAddress': toAddress,
...extra,
};