code: def test_values(self):
      result = feed_backward_comb_filter(sig_1d, 2, 0.5)
      self.assertTrue(np.allclose(result, res_1d_bw_2))
      result = feed_backward_comb_filter(sig_1d, 3, 0.5)
      self.assertTrue(np.allclose(result, res_1d_bw_3))
      result = feed_backward_comb_filter(sig_2d, 2, 0.5)
      self.assertTrue(np.allclose(result, res_2d_bw_2))
      result = feed_backward_comb_filter(sig_2d, 3, 0.5)
      self.assertTrue(np.allclose(result, res_2d_bw_3))
  
imports: from __future__ import absolute_import, division, print_function
  import unittest
  from madmom.audio.comb_filters import *
label_desc: Use image node_id 2 for calling the TestFeedBackwardFilterFunction obj's underlying member method code with example usage: obj.test_values() without return types