[ExtendScript] How to determine if a ProjectItem is a sub-clip?

I couldn't find a straight-forward way of determining whether a ProjectItem is a subclip.

One way could be is to utilize "ignoreSubCLips" flag of "findItemsMatchingMediaPath", but I can't use that in my solution since I couldn't provide a "pathToMatch" parameter on that part of the code.

What is the best way to do this?