Pull out the meta data plate value and put it into the instance value
        :param meta_data: the original meta data
        :param instance: the original instance
        :return: the modified instance

def mapper(self, meta_data, instance):
        """
        Pull out the meta data plate value and put it into the instance value
        :param meta_data: the original meta data
        :param instance: the original instance
        :return: the modified instance
        """
        d = dict(meta_data)
        v = d.pop(self.aggregation_meta_data)
        instance = deepcopy(instance)
        instance.value[self.aggregation_meta_data] = v
        return instance