code: def test_sum(self, xp, sp):
      m = _make(xp, sp, self.dtype)
      return m.sum(axis=self.axis, dtype=self.ret_dtype)
  
imports: import pickle
  import unittest
  import numpy
  import pytest
  import cupy
  from cupy import testing
  from cupy.cuda import driver
  from cupy.cuda import runtime
  from cupyx.scipy import sparse
label_desc: Use image node_id 2 for calling the TestDiaMatrixSum obj's underlying member method code with example usage: obj.test_sum(xp, sp) and returns: m