I got stuck here too. I was able to implement most of them, but I’m confused by new_graph/1.
I assume that new_graph/2 is a straightforward wrapper around GraphCommons.Graph.new. I would guess that new_graph/1 is derived from new_graph/2 via some default value for one of the arguments of GraphCommons.Graph.new, but it has no default values.
Re your NB, the MixProject module is defined in apps/native_graph/mix.exs, which was generated by
$ mix new native_graph.