code: def test_multiple_trackers():
      tracker1 = Tracker(
          "euclidean",
          initialization_delay=0,
          distance_threshold=1,
          hit_counter_max=2,
      )
      tracker2 = Tracker(
          "euclidean",
          initialization_delay=0,
          distance_threshold=1,
          hit_counter_max=2,
      )
      detections1 = [Detection(points=np.array([[1, 1]]))]
      detections2 = [Detection(points=np.array([[2, 2]]))]
  
      tracked_objects1 = tracker1.update(detections1)
      assert len(tracked_objects1) == 1
      tracked_objects2 = tracker2.update(detections2)
      assert len(tracked_objects2) == 1
  
      assert tracker1.total_object_count == 1
      assert tracker2.total_object_count == 1
  
file_path: norfair/tests/test_tracker.py
imports: import numpy
  import pytest
  from norfair import Detection, FilterPyKalmanFilterFactory, OptimizedKalmanFilterFactory, Tracker
  from norfair.utils import validate_points
label_desc: Use image node_id 8 for calling a global function with example usage: test_multiple_trackers() without return types