def test_saveUnPersistableThenFormat(self):
        """
        Saving and loading an object which cannot be represented in JSON, but
        has a string representation which I{can} be saved as JSON, will result
        in the same string formatting; any extractable fields will retain their
        data types.
        """
        class Reprable(object):
            def __init__(self, value):
                self.value = value

            def __repr__(self):
                return("reprable")

        inputEvent = {
            "log_format": "{object} {object.value}",
            "object": Reprable(7)
        }
        outputEvent = eventFromJSON(self.savedEventJSON(inputEvent))
        self.assertEqual(formatEvent(outputEvent), "reprable 7")

        Saving and loading an object which cannot be represented in JSON, but
        has a string representation which I{can} be saved as JSON, will result
        in the same string formatting; any extractable fields will retain their
        data types.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/logger/test/test_json.py