def process(parsed_files, opts)
      r = aggregate(parsed_files)
      r = pre_process(r, opts)
      r = to_class_objects(r, opts)
      return post_process(r, opts)
    end
def process(parsed_files, opts)
      r = aggregate(parsed_files)
      r = pre_process(r, opts)
      r = to_class_objects(r, opts)
      return post_process(r, opts)
    end
Processes array of Source::File objects from BatchParser and
 returns instance of Relations class.