code: def testNullValue(self):
      self.assertEqual(Flatness()([1, 2, 5, 3, 5.7, 0, 2, 6, 8]), 0)
  
file_path: essentia/test/src/unittests/stats/test_flatness.py
imports: from essentia_test import *
label_desc: Use image node_id 4 for calling the TestFlatness obj's underlying member method code with example usage: obj.testNullValue() without return types