code: def test_add_background_noise(self):
      self.evaluate_function(
          audaugs.add_background_noise,
          background_audio=None,
          snr_level_db=10.0,
      )
  
imports: import unittest
  from augly import audio
  from augly.tests.audio_tests.base_unit_test import BaseAudioUnitTest
label_desc: Use image node_id 1 for calling the FunctionalAudioUnitTest obj's underlying member method code with example usage: obj.test_add_background_noise() without return types