code: def test_nonzero_bits(self):
      mask = BitMask.from_bin("0b0")
      indices = [100, 1000, 10_000, 100_000]
  
      self.assertEqual(mask.x, 0)
      for index in indices:
          mask.set_kth_bit(index)
  
      self.assertGreaterEqual(mask.x, 0)
      also_indices = mask.to_indices()
  
      for i, j in zip(indices, also_indices):
          self.assertEqual(i, j)
  
imports: import unittest
  from copy import deepcopy
  from random import randint, random, seed
  from lightly.api.bitmask import BitMask
label_desc: Use image node_id 19 for calling the TestBitMask obj's underlying member method code with example usage: obj.test_nonzero_bits() without return types