docs: def upload_files(self, abspaths, relpaths, remote_objects):
          """
          Determines files to be uploaded and call ``upload_file`` on each.
          """
          for relpath in relpaths:
              abspath = [p for p in abspaths if p[len(self.file_root):] == relpath][0]
              cloud_datetime = remote_objects[relpath] if relpath in remote_objects else None
              local_datetime = datetime.datetime.utcfromtimestamp(os.stat(abspath).st_mtime)
  
              if cloud_datetime and local_datetime < cloud_datetime:
                  self.skip_count += 1
                  if not self.quiet:
                      print("Skipped {0}: not modified.".format(relpath))
                  continue
              if relpath in remote_objects:
                  self.update_count += 1
              else:
                  self.create_count += 1
              self.upload_file(abspath, relpath)