How to delete a file from FileRepository in Java extension?

I have a Java extension where I need to write a service that deletes a specified file from MyCustomFileRepository.

But the DeleteFile method isn't available as part of the FileRepositoryThing class!

@ThingworxServiceDefinition(name = "DeleteFile", description = "Deletes the specified file from the Healthband FileRepository entity.", category = "", isAllowOverride = false, aspects = {"isAsync:false" })
@ThingworxServiceResult(name = "Result", description = "", baseType = "STRING", aspects = {})
public String DeleteFile(
        @ThingworxServiceParameter(name = "filePath", description = "", baseType = "STRING", aspects = {"isRequired:true" }) String filePath) {
    final FileRepositoryThing repo = (FileRepositoryThing) ThingUtilities.findThing("MyCustomFileRepository");
    repo.DeleteFile(filePath);
    return "";
}
}