private NavigationItem ParseListItemBlock(ListItemBlock listItemBlock)
{
DisplayLink rootLink = default;
List <NavigationItem> children = new List <NavigationItem>();
foreach (var listItemChild in listItemBlock)
{
switch (listItemChild)
{
case ParagraphBlock paragraphBlock:
rootLink = ParseParagraph(paragraphBlock);
break;
case ListBlock listBlock:
children.AddRange(ParseListBlock(listBlock));
break;
default:
throw new InvalidOperationException(
$"Document contains invalid navigation document syntax at {listItemBlock.ToPositionText()}. Expected paragraph.");
}
}
if (rootLink.Equals(default(DisplayLink)))
{
return(default);
