Problem: in-n-out of the mta system in this problem, we will have a brief introduction to how data structures in computer science work. if you’ve ever used any transit app to get directionsin the nyc subway system, you probably were given either direct subway routes or directions to transfer at specific stops to other subway lines. these apps use data listing all the subway stations on each subway line and data about which stations have transfersfrom which line to which other line(s). don’t worry about details of how these apps work. in this homework, you’ll write a program that deals with one aspect of such apps -- looking into the subway system with a python program that reads and analyzes data from a given data file similar to those supplied by the mta. your task is to design and write a program that will repeatedly ask the user for a train line until he/she enters ‘done’. for each train line input the program should print out the stops of that train.