Loads/dumps variant type
        :param elem:
        :param elem_type:
        :param params:
        :return:

async def variant(self, elem=None, elem_type=None, params=None):
        """
        Loads/dumps variant type
        :param elem:
        :param elem_type:
        :param params:
        :return:
        """
        elem_type = elem_type if elem_type else elem.__class__
        version = await self.version(elem_type, params, elem=elem)

        if self.is_tracked():
            return self.get_tracked()

        if hasattr(elem_type, 'boost_serialize'):
            elem = elem_type() if elem is None else elem
            self.pop_track()
            return await elem.boost_serialize(self, elem=elem, elem_type=elem_type, params=params, version=version)

        if self.writing:
            self.pop_track()
            return await self.dump_variant(elem=elem,
                                           elem_type=elem_type if elem_type else elem.__class__, params=params)
        else:
            obj = await self.load_variant(elem_type=elem_type if elem_type else elem.__class__,
                                          params=params, elem=elem)
            return self.track_obj(obj)