getRegion(name, atlas) {
		let region;
		if (typeof atlas === "string") {
			region = this.getAtlas(atlas)[name];
		} else {
			// look for the given region in each existing atlas
			for (const atlas of this.atlases.values()) {
				if (typeof atlas[name] !== "undefined") {
					// there should be only one
					region = atlas[name];
					break;
				}
			}
		}
		return region;
	}
return a normalized region (or frame) information for the specified sprite name
@param {string} name - name of the sprite
@param {string} [atlas] - name of a specific atlas where to search for the region
@returns {object}