code: def test_single_value_dunder_all():
      """Test that single value __all__ is parsed correctly."""
      parser = Parser()
      code = CodeSnippet(
          """\
          __all__ = 'foo',
      """
      )
      module = parser.parse(code, "filepath")
      assert module.dunder_all == ("foo",)
  
      code = CodeSnippet(
          """\
          __all__ = 'foo'
      """
      )
      module = parser.parse(code, "filepath")
      assert module.dunder_all is None
      assert module.dunder_all_error
  
      code = CodeSnippet(
          """\
          __all__ = ('foo', )
      """
      )
      module = parser.parse(code, "filepath")
      assert module.dunder_all == ("foo",)
  
imports: import io
  import sys
  import pytest
  import textwrap
  from pathlib import Path
  from pydocstyle.parser import Parser, ParseError
label_desc: Use image node_id 21 for calling a global function with example usage: test_single_value_dunder_all() without return types