Invert the keys and values of an object.
        The values must be serializable.

def invert(self):
        """
        Invert the keys and values of an object.
        The values must be serializable.
        """
        keys = self._clean.keys()
        inverted = {}
        for key in keys:
            inverted[self.obj[key]] = key

        return self._wrap(inverted)