How to stop a sequence when certain contion is matched?
![kmax-event-file-structure](https://user-images.githubusercontent.com/93395/40593421-0fb8d9ac-625b-11e8-9ee9-07520bda9c56.png)
As the attached picture, a sequence might stop at certain condition, e.g., when encountering some magic or next block is not the same data type. How to depict this kind of conditional reading? How about this:
```
seq:
  - id: data_block
    type: data_type
    repeat-if: next_is_the_same_type
```