get isTrivialSnippet() {
        if (this._snippet.placeholders.length === 0) {
            return true;
        }
        if (this._snippet.placeholders.length === 1) {
            const [placeholder] = this._snippet.placeholders;
            if (placeholder.isFinalTabstop) {
                if (this._snippet.rightMostDescendant === placeholder) {
                    return true;
                }
            }
        }
        return false;
    }
A snippet is trivial when it has no placeholder or only a final placeholder at
its very end