class_docstr: Pack the inputs data for the multi object tracking and video instance
  segmentation. All the information of images are packed to ``inputs``. All
  the information except images are packed to ``data_samples``. In order to
  get the original annotaiton and meta info, we add `instances` key into meta
  keys.
  
  Args:
      meta_keys (Sequence[str]): Meta keys to be collected in
          ``data_sample.metainfo``. Defaults to None.
      default_meta_keys (tuple): Default meta keys. Defaults to ('img_id',
          'img_path', 'ori_shape', 'img_shape', 'scale_factor',
          'flip', 'flip_direction', 'frame_id', 'is_video_data',
          'video_id', 'video_length', 'instances').
code: def __init__(
      self,
      meta_keys: Optional[dict] = None,
      default_meta_keys: tuple = (
          "img_id",
          "img_path",
          "ori_shape",
          "img_shape",
          "scale_factor",
          "flip",
          "flip_direction",
          "frame_id",
          "video_id",
          "video_length",
          "ori_video_length",
          "instances",
      ),
  ):
      self.meta_keys = default_meta_keys
      if meta_keys is not None:
          if isinstance(meta_keys, str):
              meta_keys = (meta_keys,)
          else:
              assert isinstance(
                  meta_keys, tuple
              ), "meta_keys must be str or tuple"
          self.meta_keys += meta_keys
  
imports: from typing import Optional, Sequence
  import numpy
  from mmcv.transforms import to_tensor
  from mmcv.transforms.base import BaseTransform
  from mmengine.structures import InstanceData, PixelData
  from mmdet.registry import TRANSFORMS
  from mmdet.structures import DetDataSample, ReIDDataSample, TrackDataSample
  from mmdet.structures.bbox import BaseBoxes
label_desc: Use image node_id 1 to create a new PackTrackInputs object from inherited base classes: BaseTransform with example: obj = PackTrackInputs(meta_keys, default_meta_keys)