class_docstr: This class represents a track/tracklet used in the SMOT Tracker
  It has the following properties
  
  *******************************************************
  mean: 4-tuple representing the (x0, y0, x1, y1) as the current state (location) of the tracked object
  track_id: the numerical id of the track
  age: the number of timesteps since its first occurrence
  time_since_update: number of time-steps since the last update of the its location
  state: the state of the track, can be one in `TrackState`
  confidence_score: tracking_confidence at the current timestep
  
  source: a tuple of (anchor_indices, anchor_weights)
  attributes: np.ndarray of additional attributes of the object
  *******************************************************
  
  It also has these configs
  keep_alive_thresh: the minimal tracking/detection confidence to keep the track in Active state
  max_missing: the maximal timesteps we will keep searching for this track when missing before we mark it as deleted
  *******************************************************
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code: def link_to(self, track):
      self.linked_id = track.display_id
  
imports: import time
  import logging
  from contextlib import contextmanager
  import mxnet
  import numpy
label_desc: Use image node_id 4 for calling the Track obj's underlying member method code with example usage: obj.link_to(track) without return types