code: def test_len(self):
      for sp in (scipy.sparse, sparse):
          s = self.dummy_class(sp)()
          with pytest.raises(TypeError):
              len(s)
  
file_path: cupy/tests/cupyx_tests/scipy_tests/sparse_tests/test_base.py
imports: import unittest
  import pytest
  from cupy import testing
  from cupyx.scipy import sparse
label_desc: Use image node_id 3 for calling the TestSpmatrix obj's underlying member method code with example usage: obj.test_len() without return types