Pass Optional argument while creating library

I am creating a custom activity of click, which will First check, whether the element exists or not then if it exists, it will click on this.
Here I want to pass optional argument i.e. user can pass either element or selector, however when trying to do that getting an error that only one argument can be passed.

Is it possible to pass an optional argument, if yes how can I do this?
Please help me out.

Got Resolved. Thanks

how? please explain.

I also Want to create an optional argument.

@gupta.rak1984, how you resolved ? can you please explain?