Clarify that asyncio.Server.sockets is a socket-like TransportSocket
:meth:`loop.create_unix_server`, :func:`start_server`,
and :func:`start_unix_server` functions.
-Do not instantiate the class directly.
+Do not instantiate the :class:`Server` class directly.
.. class:: Server
.. attribute:: sockets
- List of :class:`socket.socket` objects the server is listening on.
+ List of socket-like objects, ``asyncio.trsock.TransportSocket``, which
+ the server is listening on.
.. versionchanged:: 3.7
Prior to Python 3.7 ``Server.sockets`` used to return an