code: def _test_plot_confusion_matrix(backend):
      dataset = foz.load_zoo_dataset("quickstart")
      results = dataset.evaluate_detections(
          "predictions",
          gt_field="ground_truth",
          classwise=False,
          eval_key="eval",
      )
  
      counts = dataset.count_values("ground_truth.detections.label")
      classes = sorted(counts, key=counts.get, reverse=True)[:10]
  
      plot = results.plot_confusion_matrix(
          classes=classes, backend=backend
      )
      plot.show()
  
      input("Press enter to continue...")
  
imports: import random
  import unittest
  import numpy
  import fiftyone
  import fiftyone.brain
  import fiftyone.zoo
  from fiftyone import ViewField
label_desc: Use image node_id 27 for calling a global function with example usage: _test_plot_confusion_matrix(backend) without return types