code: def test_forward_cpu(self):
      self.check_forward(self.diag, self.non_diag, gpu=-1)
  
file_path: pfrl/tests/functions_tests/test_lower_triangular_matrix.py
imports: import numpy
  import pytest
  import torch
  from pfrl.functions.lower_triangular_matrix import lower_triangular_matrix
label_desc: Use image node_id 3 for calling the TestLowerTriangularMatrix obj's underlying member method code with example usage: obj.test_forward_cpu() without return types