old_contents: import unittest
  
  import numpy as np
  
  from chainer import testing
  from chainercv.transforms import non_maximum_suppression
  
  
  @testing.parameterize(
      {'threshold': 1, 'expect': (True, True, True, True)},
      {'threshold': 0.5, 'expect': (True, True, False, True)},
      {'threshold': 0.3, 'expect': (True, True, False, False)},
      {'threshold': 0.2, 'expect': (True, False, False, False)},
  )
  class TestNonMaximumSuppression(unittest.TestCase):
  
      def setUp(self):
          self.bbox = np.array((
              (1, 2, 3, 4),
              (0, 1, 4, 5),  # 4/16
              (1, 2, 3, 5),  # 4/6, 6/16
              (1, 2, 5, 6),  # 6/16, 9/23, 4/16
          ))
          self.expect = np.array(self.expect)
  
      def test_non_maximum_suppression(self):
          out = non_maximum_suppression(self.bbox, self.threshold)
          np.testing.assert_equal(out, self.bbox[self.expect])
  
      def test_non_maximum_suppression_param(self):
          out, param = non_maximum_suppression(
              self.bbox, self.threshold, return_param=True)
          np.testing.assert_equal(param['selection'], self.expect)
          np.testing.assert_equal(out, self.bbox[param['selection']])
  
  
  testing.run_module(__name__, __file__)
  
new_contents: import unittest
  
  import numpy as np
  
  from chainer import testing
  from chainercv.transforms import non_maximum_suppression
  
  
  @testing.parameterize(
      {'threshold': 1, 'expect': (True, True, True, True)},
      {'threshold': 0.5, 'expect': (True, True, False, True)},
      {'threshold': 0.3, 'expect': (True, False, True, True)},
      {'threshold': 0.2, 'expect': (True, False, False, True)},
      {'threshold': 0, 'expect': (True, False, False, False)},
  )
  class TestNonMaximumSuppression(unittest.TestCase):
  
      def setUp(self):
          self.bbox = np.array((
              (0, 0, 4, 4),
              (1, 1, 5, 5),  # 9/23
              (2, 1, 6, 5),  # 6/26, 12/20
              (4, 0, 8, 4),  # 0/32, 3/29, 6/26
          ))
          self.expect = np.array(self.expect)
  
      def test_non_maximum_suppression(self):
          out = non_maximum_suppression(self.bbox, self.threshold)
          np.testing.assert_equal(out, self.bbox[self.expect])
  
      def test_non_maximum_suppression_param(self):
          out, param = non_maximum_suppression(
              self.bbox, self.threshold, return_param=True)
          np.testing.assert_equal(param['selection'], self.expect)
          np.testing.assert_equal(out, self.bbox[param['selection']])
  
  
  testing.run_module(__name__, __file__)
  
subject: improve tests