added list, retrieve and update functions
added list, retrieve and update functions

ilanasufrin/nyu-devops-homework-1,Cantal0p3/nyu-devops-homework-1,ilanasufrin/nyu-devops-homework-1,Cantal0p3/nyu-devops-homework-1,ilanasufrin/nyu-devops-homework-1,Cantal0p3/nyu-devops-homework-1