code: def check_forward(self, x_data):
      y = distributions.multivariate_normal._triangular_inv(
          x_data, lower=self.lower
      )
      inv_x = numpy.linalg.inv(cuda.to_cpu(x_data))
      testing.assert_allclose(y.array, inv_x)
  
imports: import unittest
  import numpy
  from chainer import cuda
  from chainer import distributions
  from chainer import gradient_check
  from chainer import testing
  from chainer.testing import attr
label_desc: Use image node_id 2 for calling the TestTriangularInv obj's underlying member method code with example usage: obj.check_forward(x_data) without return types