The goal of this snippet is to extract "transactions", this could be any object which has a date in it or any other indicator but this will be using date.

this getter will have no argument because it's a getter.

it will return a list of Transaction objects.

we are filtering _transactions using the "where", where takes in (element) in here we are only using the first argument, element.

elements will be items in the transactions, each element will have a date and the date is a dart DateTime type. 

so we can use flutter methods of isAfter and subtract. 

finally, once the filter is complete we want to explicitly convert it to a list using toList()

  List<Transaction> get _recentTransactions {
    return _transactions.where((element) {
      return element.date.isAfter(
        DateTime.now().subtract(
          Duration(days: 7),
        ),
      );
    }).toList();
 }