code: def test_read_undefined(self):
      with self.assertRaisesRegex(
          UnboundLocalError, "used before assignment"
      ):
          variables.ld(variables.Undefined("a"))
  
imports: import unittest
  from nvidia.dali._autograph.operators import variables
label_desc: Use image node_id 4 for calling the SpecialValuesTest obj's underlying member method code with example usage: obj.test_read_undefined() without return types