code: def test_len(c=BitSet):
      b = c()
      b.add(3)
      b.add(5)
      b.add(1024)
      assert len(b) == 3
      b.add(5)
      assert len(b) == 3
      b.discard(1000)
      assert len(b) == 3
      b.discard(5)
      assert len(b) == 2
  
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 2 for calling a global function with example usage: test_len(c) without return types