def accept(item) {
   return item.status == 'Successful'
}

All Failed builds

def accept(item) {
    return item.status == 'Failed'
}

New build today ?

def accept(item) {
   return util.today(item.started)
}

All Failed builds this week

def accept(item) {
   return util.thisWeek(item.finished) && item.status == 'Failed'
}