code: def connection_made(self, transport: asyncio.BaseTransport) -> None:
          
          if self._stream_reader is None:
              raise SMTPServerDisconnected("Client not connected")
  
          self._stream_reader._transport = transport  # type: ignore
          self._over_ssl = transport.get_extra_info("sslcontext") is not None
          self._stream_writer = asyncio.StreamWriter(
              transport, self, self._stream_reader, self._loop
          )
          self._client_connected_cb(  # type: ignore
              self._stream_reader, self._stream_writer
          )
docs: Modified ``connection_made`` that supports upgrading our transport in
          place using STARTTLS.
  
          We set the _transport directly on the StreamReader, rather than calling
          set_transport (which will raise an AssertionError on upgrade).