code: def test_sparse_vectorss():
      svss = sparse_vectorss()
      assert len(svss) == 0
  
      svss.resize(5)
      for svs in svss:
          assert len(svs) == 0
  
      svss.clear()
      assert len(svss) == 0
  
      svss.extend(
          [
              sparse_vectors(
                  [
                      sparse_vector([pair(1, 2), pair(3, 4)]),
                      sparse_vector([pair(5, 6), pair(7, 8)]),
                  ]
              )
          ]
      )
  
      assert len(svss) == 1
      assert svss[0][0][0].first == 1
      assert svss[0][0][0].second == 2
      assert svss[0][0][1].first == 3
      assert svss[0][0][1].second == 4
      assert svss[0][1][0].first == 5
      assert svss[0][1][0].second == 6
      assert svss[0][1][1].first == 7
      assert svss[0][1][1].second == 8
  
      deser = pickle.loads(pickle.dumps(svss, 2))
      assert deser == svss
  
imports: from dlib import pair, make_sparse_vector, sparse_vector, sparse_vectors, sparse_vectorss
  from pytest import approx
label_desc: Use image node_id 4 for calling a global function with example usage: test_sparse_vectorss() without return types