Write a python program words.py that reads either a text file or a text from stdin and writes to stdout,all the unique words in the input in alphabetical order (one per line.)

The program should be set up in such a way that if the program gets a command line argument, it expects it to be a file name, and, if not, it reads input from stdin. Please use a file name as an example for learning purposes. I will love to get a detailed example of how this process works as I am new to using python in command line.