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 __repr__(self) -> str:
      repr_str = self.__class__.__name__
      repr_str += f"meta_keys={self.meta_keys}, "
      repr_str += f"default_meta_keys={self.default_meta_keys})"
      return repr_str
  
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 3 for calling the PackTrackInputs obj's underlying member method code with example usage: obj.__repr__() and returns: repr_str