def _finishInit(self, whenDone, skt, error, reactor):
        """
        Called by subclasses to continue to the stage of initialization where
        the socket connect attempt is made.

        @param whenDone: A 0-argument callable to invoke once the connection is
            set up.  This is L{None} if the connection could not be prepared
            due to a previous error.

        @param skt: The socket object to use to perform the connection.
        @type skt: C{socket._socketobject}

        @param error: The error to fail the connection with.

        @param reactor: The reactor to use for this client.
        @type reactor: L{twisted.internet.interfaces.IReactorTime}
        """
        if whenDone:
            self._commonConnection.__init__(self, skt, None, reactor)
            reactor.callLater(0, whenDone)
        else:
            reactor.callLater(0, self.failIfNotConnected, error)

        Called by subclasses to continue to the stage of initialization where
        the socket connect attempt is made.

        @param whenDone: A 0-argument callable to invoke once the connection is
            set up.  This is L{None} if the connection could not be prepared
            due to a previous error.

        @param skt: The socket object to use to perform the connection.
        @type skt: C{socket._socketobject}

        @param error: The error to fail the connection with.

        @param reactor: The reactor to use for this client.
        @type reactor: L{twisted.internet.interfaces.IReactorTime}
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/tcp.py