code: func (s *Store) TrackValue(key string, value interface{}) {
  	if !s.calculateHints {
  		return
  	}
  
  	s.diffmu.Lock()
  	var (
  		d     *diff
  		found bool
  	)
  
  	d, found = s.diffs[key]
  
  	if !found {
  		d = &diff{}
  		s.diffs[key] = d
  	}
  
  	d.add(value)
  	s.diffmu.Unlock()
  }
docs: // TrackValue tracks the value for diff calculations etc.