code: def test_empty_sample(self):
      # test sample with empty string and empty list
      self.assertRaises(AttributeError, sm_numword.transform, "")
      self.assertRaises(AttributeError, sm_numword.transform, [])
  
imports: import unittest
  from textflint.input.component.sample.sm_sample import SMSample
  from textflint.generation.transformation.SM import SwapNum
label_desc: Use image node_id 3 for calling the TestSwapNum obj's underlying member method code with example usage: obj.test_empty_sample() without return types