querySelectorAll(query) {
    query = query.toUpperCase(); // @ts-ignore

    return Array.from(new YXmlTreeWalker(this, element => element.nodeName && element.nodeName.toUpperCase() === query));
  }
Returns all YXmlElements that match the query.
Similar to Dom's {@link querySelectorAll}.

@todo Does not yet support all queries. Currently only query by tagName.

@param {CSS_Selector} query The query on the children
@return {Array<YXmlElement|YXmlText|YXmlHook|null>} The elements that match this query.

@public