code: def check_DNSP_forward(self, a_data, b_data, atol=1e-4, rtol=1e-5):
      a = chainer.Variable(a_data)
      sp_b = utils.to_coo(b_data, requires_grad=True)
      c = F.sparse_matmul(
          a, sp_b, transa=self.transa, transb=self.transb
      )
      testing.assert_allclose(self.forward_answer, c.data, atol, rtol)
  
imports: import unittest
  import numpy
  import chainer
  from chainer import cuda
  import chainer.functions
  from chainer import gradient_check
  from chainer import testing
  from chainer.testing import attr
  from chainer import utils
  from chainer.utils import type_check
label_desc: Use image node_id 13 for calling the TestCooMatMul obj's underlying member method code with example usage: obj.check_DNSP_forward(a_data, b_data, atol, rtol) without return types