code: def test_double_fault():
      labels = np.array([0, 0, 0, 0, 1, 1, 1])
      pred1 = np.array([1, 0, 1, 0, 0, 0, 0])
      pred2 = np.array([1, 0, 0, 0, 1, 0, 0])
  
      actual = double_fault(labels, pred1, pred2)
  
      assert actual == 3.0 / 7
  
imports: import sys
  import numpy
  import pytest
  from deslib.util.diversity import _process_predictions, double_fault, Q_statistic, ratio_errors, agreement_measure, disagreement_measure, correlation_coefficient
label_desc: Use image node_id 12 for calling a global function with example usage: test_double_fault() without return types