def METHOD_NAME(self, batch):
    class_labels = [] 
    event_time_max = [] 
    event_time_min = [] 
    for i, class_samples in enumerate(batch):
        for sample in class_samples:
            max_time = max(sample[self.col_time])
            min_time = min(sample[self.col_time])
            event_time_max.append(max_time)
            event_time_min.append(min_time)
            class_labels.append(i)
    return class_labels, event_time_max, event_time_min