How to check if documents exist?

Hi there, I am trying to create an expression rule that returns true if a document is not null, and has an ID attached to it. The expression rule is used to determine an XOR node to go to the document deletion node to delete the document if it exists, or to move to the end node if it has already been deleted. Right now, I am using a plugin isObjectExists() and it does work correctly but my supervisor wants me to improve the code to not use that plugin, any ideas for what to do?

Here is the expression rule I created, it currently works how I want it to but I want to avoid using the plugin, any help is appreciated!