code: def test_empty_input(self):
      audio = np.array([])
      aug = naa.CropAug(sampling_rate=self.sampling_rate)
      augmented_data = aug.augment(audio)
  
      self.assertTrue(np.array_equal(audio, augmented_data))
  
file_path: nlpaug/test/augmenter/audio/test_crop.py
imports: import unittest
  import os
  import numpy
  from dotenv import load_dotenv
  import nlpaug.augmenter.audio
  from nlpaug.util import AudioLoader
label_desc: Use image node_id 2 for calling the TestCrop obj's underlying member method code with example usage: obj.test_empty_input() without return types