Unfamiliar Territory

As I am not used to working with code I have not written, I am working on a visual diagram of the subprocess functions to give me an idea of the general stack trace for functions as they are called. It will give me something I can physically reference without having to backtrack while I am in the middle of coding. My first addition to the subprocess module is to be able to treat the subprocess objects like file I/O objects so that write and read and readlines can be used however as this was not in my initial proposal I would like some feedback and criticism.