class_docstr: Tracker for OC-SORT.
  
  Args:
      motion (dict): Configuration of motion. Defaults to None.
      obj_score_thrs (float): Detection score threshold for matching objects.
          Defaults to 0.3.
      init_track_thr (float): Detection score threshold for initializing a
          new tracklet. Defaults to 0.7.
      weight_iou_with_det_scores (bool): Whether using detection scores to
          weight IOU which is used for matching. Defaults to True.
      match_iou_thr (float): IOU distance threshold for matching between two
          frames. Defaults to 0.3.
      num_tentatives (int, optional): Number of continuous frames to confirm
          a track. Defaults to 3.
      vel_consist_weight (float): Weight of the velocity consistency term in
          association (OCM term in the paper).
      vel_delta_t (int): The difference of time step for calculating of the
          velocity direction of tracklets.
      init_cfg (dict or list[dict], optional): Initialization config dict.
          Defaults to None.
docstr: Estimate the direction vector between two boxes.
docstr_tok: ["Estimate","the","direction","vector","between","two","boxes","."]
code: def vel_direction(self, bbox1: torch.Tensor, bbox2: torch.Tensor):
      """Estimate the direction vector between two boxes."""
      if bbox1.sum() < 0 or bbox2.sum() < 0:
          return torch.tensor((-1, -1))
      cx1, cy1 = (bbox1[0] + bbox1[2]) / 2.0, (
          bbox1[1] + bbox1[3]
      ) / 2.0
      cx2, cy2 = (bbox2[0] + bbox2[2]) / 2.0, (
          bbox2[1] + bbox2[3]
      ) / 2.0
      speed = torch.tensor([cy2 - cy1, cx2 - cx1])
      norm = torch.sqrt((speed[0]) ** 2 + (speed[1]) ** 2) + 1e-6
      return speed / norm
  
imports: from typing import List, Optional, Tuple
  import numpy
  import torch
  from addict import Dict
  from mmengine.structures import InstanceData
  from mmdet.registry import MODELS
  from mmdet.structures import DetDataSample
  from mmdet.structures.bbox import bbox_cxcyah_to_xyxy, bbox_overlaps, bbox_xyxy_to_cxcyah
  from .sort_tracker import SORTTracker
label_desc: Use image node_id 5 for calling the OCSORTTracker obj's underlying member method code with example usage: obj.vel_direction(bbox1, bbox2) and returns: unknown, torch