code: def _get_candidate_names():
      
  
      global _name_sequence
      if _name_sequence is None:
          _once_lock.acquire()
          try:
              if _name_sequence is None:
                  _name_sequence = _RandomNameSequence()
          finally:
              _once_lock.release()
      return _name_sequence
docs: Common setup sequence for all user-callable interfaces.