code: def test_types(self):
      function = feed_backward_comb_filter
      result = comb_filter(sig_1d, function, [2, 3], [0.5, 0.5])
      self.assertIsInstance(result, np.ndarray)
      self.assertTrue(type(result), float)
      function = feed_forward_comb_filter
      result = comb_filter(sig_1d, function, [2, 3], [0.5, 0.5])
      self.assertIsInstance(result, np.ndarray)
      self.assertTrue(type(result), float)
  
imports: from __future__ import absolute_import, division, print_function
  import unittest
  from madmom.audio.comb_filters import *
label_desc: Use image node_id 1 for calling the TestCombFilterFunction obj's underlying member method code with example usage: obj.test_types() without return types