code: def test_empty_path(self):
      # beat activation which leads to an empty path
      act = np.array([0, 1, 0, 1, 0, 1])
      self.assertTrue(np.allclose(self.processor(act), []))
  
imports: from __future__ import absolute_import, division, print_function
  import unittest
  from os.path import join
  from madmom.ml.hmm import HiddenMarkovModel
  from madmom.audio.signal import FramedSignal
  from madmom.features import Activations
  from madmom.features.beats import *
  from madmom.features.beats_hmm import *
  from .None import AUDIO_PATH, ACTIVATIONS_PATH
label_desc: Use image node_id 6 for calling the TestDBNBeatTrackingProcessorClass obj's underlying member method code with example usage: obj.test_empty_path() without return types