def test_DownArrowToPartialLineInHistory(self):
        """
        Pressing down arrow to visit an entry that was added to the
        history by pressing the up arrow instead of return does not
        raise a L{TypeError}.

        @see: U{http://twistedmatrix.com/trac/ticket/9031}

        @return: A L{defer.Deferred} that fires when C{b"done"} is
            echoed back.
        """

        return self._trivialTest(
            b"first line\n" + b"partial line" + up + down + b"\ndone",
            [b">>> first line",
             b"first line",
             b">>> partial line",
             b"partial line",
             b">>> done"])

        Pressing down arrow to visit an entry that was added to the
        history by pressing the up arrow instead of return does not
        raise a L{TypeError}.

        @see: U{http://twistedmatrix.com/trac/ticket/9031}

        @return: A L{defer.Deferred} that fires when C{b"done"} is
            echoed back.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/test/test_recvline.py