code: async def close_all_connections(self) -> None:
          
          while self._connections:
              # Peek at an arbitrary element of the set
              conn = next(iter(self._connections))
              await conn.close()
docs: Close all open connections and asynchronously wait for them to finish.
  
          This method is used in combination with `~.TCPServer.stop` to
          support clean shutdowns (especially for unittests). Typical
          usage would call ``stop()`` first to stop accepting new
          connections, then ``await close_all_connections()`` to wait for
          existing connections to finish.
  
          This method does not currently close open websocket connections.
  
          Note that this method is a coroutine and must be caled with ``await``.