code: def test_implemented_error():
      # Attempts to save an unsupported type and checks that an
      # NotImplementedError is raised.
  
      x = dok_matrix((2, 3))
      x[0, 1] = 1
  
      assert_raises(NotImplementedError, save_npz, "x.npz", x)
  
file_path: catboost/contrib/python/scipy/py3/scipy/sparse/tests/test_matrix_io.py
imports: import os
  import numpy
  import tempfile
  from pytest import raises
  from numpy.testing import assert_equal, assert_
  from scipy.sparse import csc_matrix, csr_matrix, bsr_matrix, dia_matrix, coo_matrix, save_npz, load_npz, dok_matrix
label_desc: Use image node_id 8 for calling a global function with example usage: test_implemented_error() without return types