For this lab, you will write a Python program that will create and edit a text file called

users.txt$.$ The file should be created in the same folder as your python file and will

contain a list of usernames, with one name per line.

Your program should only define and implement the following functions:

create$\_$file$-$Accepts no arguments and creates the empty file called

users.txt

add$\_$user $-$ Accepts a username as an argument and appends it to the file

update$\_$user $-$ Accepts an old username and a new username as separate

arguments and replaces any instance of that the old username with the new

username in the file.

remove$\_$user $-$ Accepts a username as an argument and removes the user

from the file