code: def test_DNSP_sparse_matmul_double_backward_cpu(self):
      if not _scipy_available:
          return
      self.check_DNSP_double_backward(
          self.a,
          self.b,
          self.gc,
          self.gga,
          self.ggb,
          atol=1e-2,
          rtol=1e-2,
      )
  
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 20 for calling the TestCooMatMul obj's underlying member method code with example usage: obj.test_DNSP_sparse_matmul_double_backward_cpu() without return types