Data2DETR overides default method of lightning

```
 File "/home/anhtu/aloception-oss/alonet/detr/data_modules/data2detr.py", line 55, in __init__
    self.size = list(self.size)
TypeError: 'method' object is not iterable
```

The bug happens when I use `Data2Detr` class. The reason is that `size` is a method of pytorch-lightning and it is overridden here.