def test_formatWithCall(self):
        """
        L{formatWithCall} is an extended version of L{unicode.format} that
        will interpret a set of parentheses "C{()}" at the end of a format key
        to mean that the format key ought to be I{called} rather than
        stringified.
        """
        self.assertEqual(
            formatWithCall(
                u"Hello, {world}. {callme()}.",
                dict(world="earth", callme=lambda: "maybe")
            ),
            "Hello, earth. maybe."
        )
        self.assertEqual(
            formatWithCall(
                u"Hello, {repr()!r}.",
                dict(repr=lambda: "repr")
            ),
            "Hello, 'repr'."
        )

        L{formatWithCall} is an extended version of L{unicode.format} that
        will interpret a set of parentheses "C{()}" at the end of a format key
        to mean that the format key ought to be I{called} rather than
        stringified.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/logger/test/test_format.py