hunk.code_window:     if state:
           max_seq_len = torch.max(train_batch["seq_lens"])
           mask = sequence_mask(train_batch["seq_lens"], max_seq_len)
           mask = torch.reshape(mask, [-1])
       else:
           mask = torch.ones_like(
               train_batch[Postprocessing.ADVANTAGES], dtype=torch.bool)
       policy.loss_obj = PPOLoss(
           dist_class,
           model,
           train_batch[Postprocessing.VALUE_TARGETS],
  
hunk.labels: keep keep keep keep replace replace replace keep keep keep keep keep
hunk.file_path: rllib/agents/ppo/ppo_torch_policy.py
hunk.type: replace
file: Ray ID Specification
  ============================================
  ```
  
   high bits                                                                           low bits
  <--------------------------------------------------------------------------------------------
  
                                                                                     2B
                                                                            +-----------------+
                                                                            |   unique bytes  |  JobID     2B
                                                                            +-----------------+
  
                                                                   4B                2B
                                                          +-----------------+-----------------+
                                                          |   unique bytes  |       JobID     |  ActorID   6B
                                                          +-----------------+-----------------+
  
                                          8B                               6B
                              +---------------------------+-----------------------------------+
                              |       unique bytes        |               ActorID             |  TaskID   14B
                              +---------------------------+-----------------------------------+
  
         4B            2B                                  14B
  +---------------------------+---------------------------------------------------------------+
  |  index bytes  |flags bytes|                             TaskID                            |  ObjectID 20B
  +---------------------------+---------------------------------------------------------------+
  
  ```
  #### JobID (2 bytes)
  `JobID` is generated by `GCS` to ensure uniqueness. Its length is 2 bytes.
  
  #### ActorID (6 bytes)
  An `ActorID` contains two parts: 1) 4 unique bytes, and 2) its `JobID`.
  
  #### TaskID (14 bytes)
  A `TaskID` contains two parts: 1) 8 unique bytes, and 2) its `ActorID`.  
  If the task is a normal task or a driver task, the part 2 is its dummy actor id.
  
  The following table shows the layouts of all kinds of task id.
  ```
  +-------------------+-----------------+------------+---------------------------+-----------------+
  |                   | Normal Task     | Actor Task | Actor Creation Task       | Driver Task     |
  +-------------------+-----------------+------------+---------------------------+-----------------+
  | task unique bytes | random          | random     | nil                       | nil             |
  +-------------------+-----------------+------------+---------------------------+-----------------+
  | actor id          | dummy actor id* | actor id   | Id of the actor to create | dummy actor id* |
  +-------------------+-----------------+------------+---------------------------+-----------------+
  Note: Dummy actor id is an `ActorID` whose unique part is nil.
  ```
  
  #### ObjectID (20 bytes)
  An `ObjectID` contains 3 parts:
  - `index bytes`: 4 bytes to indicate the index of the object.
  - `flags bytes`: 2 bytes to indicate the flags of this object. We have 3 flags now: `created_by_task`, `object_type` and `transport_type`.
  - `TaskID`: 14 bytes to indicate the ID of the task to which this object belongs.
  
  **flags bytes format**
  ```
    1b     1b        3b                          11b
  +-------------------------------------------------------------------------+
  | (1) | (2) |     (3)      |                (4)unused                     |
  +-------------------------------------------------------------------------+
  ```
  - The (1) `created_by_task` part is one bit to indicate whether this `ObjectID` is generated (put or returned) from a task.
  
  - The (2) `object_type` part is one bit to indicate the type of this object, whether a `PUT_OBJECT` or a `RETURN_OBJECT`.
      - `PUT_OBJECT` indicates this object is generated through `ray.put` during the task's execution.
      - `RETURN_OBJECT` indicates this object is the return value of a task.
  
  - The (3) `transport_type` part is 3 bits to indicate the type of the transport which is used to transfer this object. So it can support 8 types.
  
  - There are 11 bits unused in `flags bytes`.
  