Two API, 'mindrecord_task_number' and 'mindrecord_dict_data', must be implemented
- 'mindrecord_task_number()' returns number of tasks. Return 1 if data row is generated serially. Return N if generator can be split into N parallel-run tasks.
- 'mindrecord_dict_data(task_id)' yields dictionary data row by row. 'task_id' is 0..N-1, if N is return value of mindrecord_task_number()
Tricky for parallel run
- For imagenet, one directory can be a task.
- For TFRecord with multiple files, each file can be a task.
- For TFRecord with 1 file only, it could also be split into N tasks. Task_id=K means: data row is picked only if (count % N == K)