Here is an example of how I might structure this

[datapimp]

Notice how I use the lib folder, and how i use a module to namespace stuff.

Also notice how the Card is not coupled at all to any interface.

I stubbed out the BulkValidator class which you could interact with from the command line. If you wanted to validate a bunch of cards from the command line, or pipe a CSV of card data to your tool, etc.

I haven't ran this code or tested it, it is just for illustration purposes