How to see function calls?

When debuging a function it's often helpful to have a log of all the functions that are being called when running a specific functions. At the moment I'm using a lot of `IO.inspect` which is good but tedious when a lot of functions are called.

I think the `dbg` module of Erlang can be used to trace the function calls: http://erlang.org/doc/man/dbg.html

see also https://stackoverflow.com/questions/50364530/elixir-trace-function-call and https://stackoverflow.com/questions/1954894/using-trace-and-dbg-in-erlang/1954980#1954980