code: def test_plot_confusion_matrix(mock_plt: Mock):
      mock_plt.show = MagicMock()
  
      y_pred = [1, 1, 0, 1]
      y_true = [0, 1, 0, 1]
  
      assert plot_confusion_matrix(y_pred, y_true) is None
      mock_plt.show.assert_called_once()
  
imports: from unittest.mock import MagicMock, Mock, patch
  import numpy
  import pytest
  from chitra.visualization.metrics import cm_accuracy, detect_multilabel, plot_confusion_matrix
label_desc: Use image node_id 3 for calling a global function with example usage: test_plot_confusion_matrix(mock_plt) without return types