code: def _count_differences(self):
          
          different_items = LocalOnlyCounter(self.config.upload_bytes_per_chunk)
          different_items.walk_project(self.local_project)
          return different_items
docs: Count how many things we will be sending.
          :param local_project: LocalProject project we will send data from
          :return: LocalOnlyCounter contains counts for various items