configure(options, dataUrl, postData) {
        return options;
    }
@function
@param {Object} options - the options
@param {String} dataUrl - the url the image was retrieved from, if any.
@param {String} postData - HTTP POST data in k=v&k2=v2... form or null
@returns {Object} options - A dictionary of keyword arguments sufficient
     to configure this tile sources constructor.