def set_compression(self, comp=COMP_DEFAULT, size=COMP_SIZE):
        """Override compression method (defined by container) and threshold"""
        if comp not in COMPRESSORS:
            if comp == COMP_LZ4F:
                raise ValueError('lz4f compression not available, required lz4framed')
            else:
                raise ValueError('Invalid compression method')
        if not isinstance(size, int_types) or size < 1:
            raise ValueError('size must be non-negative integer')
        self.__comp_default = comp
        self.__comp_size = size
        return self.__comp_default, self.__comp_size