class_docstr: Base class for the reference tests.
code: def test_return_possibly_undefined_legal(self, n):
      self.assertFunctionMatchesEager(return_possibly_undefined, n)
  
imports: import itertools
  from absl.testing import parameterized
  import tensorflow
  from tensorflow.python.autograph.tests import reference_test_base
label_desc: Use image node_id 3 for calling the ReferenceTest obj's underlying member method code with example usage: obj.test_return_possibly_undefined_legal(n) without return types