CBroz1

"""Coding challenge: Serial numbers | Chris Brozdowski, January 28th 2023

Goal: Create N serial numbers given N and a list of valid characters for each position 
    in the resulting serial. 

Assumptions:
    1. Each item in the list will be a string.
    2. If a provided string is empty, there are no valid characters for this position. 
        Output should exclude this position.
    3. If N exceeds the number of unique serials, only report unique serials.