docs: def _clean_pid(self, pid):
          """if pid is a number, don't do anything. If pid is a list with one
          entry, strip the list and return the number. If pid contains more than
          one entries, do nothing.
          """
          if isinstance(pid, (list, tuple)):
              if len(pid) == 1:
                  return pid[0]
              else:
                  return pid
          return pid