code: def test_released(self):
      iter_0, iter_1 = unzip(self.iterable)
      del iter_1
  
      for i in range(20):
          next(iter_0)
  
      self.assertEqual(self.released, set(range(20)))
  
imports: import random
  import unittest
  from chainer import testing
  from chainercv.utils import unzip
label_desc: Use image node_id 2 for calling the TestUnzipRelease obj's underlying member method code with example usage: obj.test_released() without return types