How to use the autopep8.get_diff_text function in autopep8

def test_get_diff_text_without_newline(self):
        # We ignore the first two lines since it differs on Python 2.6.
        self.assertEqual(
            """\
-foo
\\ No newline at end of file
+foo
""",
            '\n'.join(autopep8.get_diff_text(['foo'],
                                             ['foo\n'],
                                             '').split('\n')[3:]))

def test_get_diff_text(self):
        # We ignore the first two lines since it differs on Python 2.6.
        self.assertEqual(
            """\
-foo
+bar
""",
            '\n'.join(autopep8.get_diff_text(['foo\n'],
                                             ['bar\n'],
                                             '').split('\n')[3:]))

formatted_source = format_code(
        source,
        aggressive=args.aggressive,
        apply_config=args.config,
        filename=filename,
        remove_all_unused_imports=args.remove_all_unused_imports,
        remove_unused_variables=args.remove_unused_variables)

    if source != formatted_source:
        if args.in_place:
            with autopep8.open_with_encoding(filename, mode='w',
                                             encoding=encoding) as output_file:
                output_file.write(formatted_source)
        else:
            diff = autopep8.get_diff_text(
                io.StringIO(source).readlines(),
                io.StringIO(formatted_source).readlines(),
                filename)
            standard_out.write(''.join(diff))

        return True

    return False