code: def DefaultSelector(sock):
      "Return the best selector for the platform"
      global _DEFAULT_SELECTOR
      if _DEFAULT_SELECTOR is None:
          if has_selector('poll'):
              _DEFAULT_SELECTOR = PollSelector
          elif hasattr(select, 'select'):
              _DEFAULT_SELECTOR = SelectSelector
          else:
              raise RedisError('Platform does not support any selectors')
      return _DEFAULT_SELECTOR(sockf DefaultSelector(sock):
      "Return the best selector for the platform"
      global _DEFAULT_SELECTOR
      if _DEFAULT_SELECTOR is None:
          if has_selector('poll'):
              _DEFAULT_SELECTOR = PollSelector
          elif hasattr(select, 'select'):
              _DEFAULT_SELECTOR = SelectSelector
          else:
              raise RedisError('Platform does not support any selectors')
      return _DEFAULT_SELECTOR(sock)
docs: Return the best selector for the platform