code: def test_union(c=BitSet):
      assert c([2, 4, 5]) | c([3, 9]) == c([2, 3, 4, 5, 9])
      b = c([2, 4, 5])
      b.update([3, 9])
      assert list(b) == [2, 3, 4, 5, 9]
      b = c([2, 4, 5])
      b.update(c([3, 9]))
      assert list(b) == [2, 3, 4, 5, 9]
      b = c([1, 2])
      b.update([1, 5, 9])
      assert list(b) == [1, 2, 5, 9]
  
file_path: whoosh/tests/test_bits.py
imports: from whoosh.filedb.filestore import RamStorage
  from whoosh.idsets import BitSet, OnDiskBitSet, SortedIntSet
label_desc: Use image node_id 3 for calling a global function with example usage: test_union(c) without return types