copy(tile, data, type) {
        const copyTransform = this.copyings[type];
        if (copyTransform) {
            const y = copyTransform(tile, data);
            return $.type(y) === "promise" ? y : $.Promise.resolve(y);
        }
        $.console.warn(`[OpenSeadragon.converter.copy] is not supported with type %s`, type);
        return $.Promise.resolve(undefined);
    }
Copy the data item given.
@param {OpenSeadragon.Tile} tile
@param {any} data data item to convert
@param {string} type data type
@return {OpenSeadragon.Promise<?>|undefined} promise resolution with data passed from constructor