'Update the stats after doing an update'

def update(self, item_count, duration_ms):

    self.total_item_count += item_count
    self.total_duration_ms += duration_ms
    self.avg_item_count += (0.1 * (item_count - self.avg_item_count))
    self.avg_duration_ms += (0.1 * (duration_ms - self.avg_duration_ms))
