function templateFactory(result) {
    let templateCache = templateCaches.get(result.type);
    if (templateCache === undefined) {
        templateCache = {
            stringsArray: new WeakMap(),
            keyString: new Map()
        };
        templateCaches.set(result.type, templateCache);
    }
    let template = templateCache.stringsArray.get(result.strings);
    if (template !== undefined) {
        return template;
    }
    // If the TemplateStringsArray is new, generate a key from the strings
    // This key is shared between all templates with identical content
    const key = result.strings.join(marker);
    // Check if we already have a Template for this key
    template = templateCache.keyString.get(key);
    if (template === undefined) {
        // If we have not seen this key before, create a new Template
        template = new Template(result, result.getTemplateElement());
        // Cache the Template for this key
        templateCache.keyString.set(key, template);
    }
    // Cache all future queries for this TemplateStringsArray
    templateCache.stringsArray.set(result.strings, template);
    return template;
}
The default TemplateFactory which caches Templates keyed on
result.type and result.strings.