def test_readlineSome(self):
        """
        Calling L{_InputStream.readline} with an integer returns at most that
        many bytes, even if it is not enough to make up a complete line.

        COMPATIBILITY NOTE: the size argument is excluded from the WSGI
        specification, but is provided here anyhow, because useful libraries
        such as python stdlib's cgi.py assume their input file-like-object
        supports readline with a size argument. If you use it, be aware your
        application may not be portable to other conformant WSGI servers.
        """
        bytes = b"goodbye\nworld"
        d = self._renderAndReturnReaderResult(
            lambda input: input.readline(3), bytes)
        d.addCallback(self.assertEqual, b"goo")
        return d

        Calling L{_InputStream.readline} with an integer returns at most that
        many bytes, even if it is not enough to make up a complete line.

        COMPATIBILITY NOTE: the size argument is excluded from the WSGI
        specification, but is provided here anyhow, because useful libraries
        such as python stdlib's cgi.py assume their input file-like-object
        supports readline with a size argument. If you use it, be aware your
        application may not be portable to other conformant WSGI servers.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_wsgi.py