I'll do my best to explain.
My plugin, at the moment, has a filename (that corresponds to a file that's located in my project). I would like the plugin to parse through the file (not the current file, but a file in my project) and retrieve all of the file's function names. It would work comparably to when you press ctrl+R (super+R on mac) and it lists the symbol definitions for the current file.
I would store the method names in a list that I will load into the autocomplete.
I hope that's a little more clarifying...