class_docstr: This class tests the functionality of `Union`.
  
  Note: It's important to be able to refine the type of a `Union` to
  one of its internal types. Currently, there are differences in the
  way Python expects `isinstance` checks and the way TorchScript
  expects `isinstance` checks. This means that we can't use
  `checkScript` in our test cases because either the eager mode or the
  script mode wouldn't run! So, some test cases have separate but
  equivalent functions to emulate `checkScript`.
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code: def test_union_type_refinement_tuple_rhs(self):
      def fn(x: int | float | List[str]) -> str:
          if isinstance(x, (int, float)):
              if isinstance(x, int):
                  return str(x)
              else:
                  return "foo"
          else:
              if len(x):
                  return x[0]
              else:
                  return "bar"
  
      self.checkScript(fn, (1,))
      self.checkScript(fn, (1.0,))
      self.checkScript(fn, (["a", "b", "c"],))
  
imports: import io
  import os
  import sys
  import unittest
  from enum import Enum
  from textwrap import dedent
  from typing import Dict, List, Optional, Tuple, Union
  import torch
  from torch.testing import FileCheck
  from torch.testing._internal.jit_utils import JitTestCase, make_global
label_desc: Use image node_id 33 for calling the TestUnion obj's underlying member method code with example usage: obj.test_union_type_refinement_tuple_rhs() and returns: str, str, x, str