getChildAttribute(node, name, attribute) {
        const child = this.findChild(node, name);
        if (child) return child.attributes && child.attributes[attribute];
    }
Get an attribute from a child node.
@param {{}} node - The parent node.
@param {string} name - The name of the child node.
@param {string} attribute - The name of the attribute.
@returns {undefined|*} The value of the attribute if found.