code: def test_sparse_sum():
      s1 = SparseNDArray(s1_data)
      v = SparseNDArray(v1, shape=(3,))
      assert s1.sum() == s1.sum()
      np.testing.assert_array_equal(
          s1.sum(axis=1), np.asarray(s1.sum(axis=1)).reshape(2)
      )
      np.testing.assert_array_equal(
          s1.sum(axis=0), np.asarray(s1.sum(axis=0)).reshape(3)
      )
      np.testing.assert_array_equal(v.sum(), np.asarray(v1_data.sum()))
  
imports: import pickle
  import numpy
  import pytest
  import scipy.sparse
  from ...None import sparse
  from ..None import SparseNDArray, SparseVector, SparseMatrix
  from ..core import issparse
label_desc: Use image node_id 13 for calling a global function with example usage: test_sparse_sum() without return types