Many documents use a specific format for a person's name. Write a function format_name that takes a single parameter name, which contains a person's full name and outputs last name followed by the initials of the first name (and middle name, if applicable). The assumption is that the last name will always be the last word in the input string. If the input is:
firstName middleName lastName
the output should be:
lastName, firstInitial. middleInitial.

>>> format_name("firstName middleName lastName") lastName, firstInitial. middleInitial.