code: function expect(element, attrName, defaultValue) {
  
      var node = angular.element(element)[0] || element;
  
      // if node exists and neither it nor its children have the attribute
      if (node &&
         ((!node.hasAttribute(attrName) ||
          node.getAttribute(attrName).length === 0) &&
          !childHasAttribute(node, attrName))) {
  
        defaultValue = angular.isString(defaultValue) ? defaultValue.trim() : '';
        if (defaultValue.length) {
          element.attr(attrName, defaultValue);
        } else if (showWarnings) {
          $log.warn('ARIA: Attribute "', attrName, '", required for accessibility, is missing on node:', node);
        }
  
      }
    }
docs: Check if expected attribute has been specified on the target element or child
  @param element
  @param attrName
  @param {optional} defaultValue What to set the attr to if no value is found