trying to add delay to server file

Servertry.py

from twisted.web.server import Site, NOT_DONE_YET
from twisted.web.resource import Resource
from twisted.internet import reactor, endpoints
from twisted.internet.task import deferLater

def getarg(request, name, default=None, type=None):
    if name in request.args:
        value = request.args[name][0]
        if type is not None:
            value = type(value)
        return value
    else:
        return default
        
class Home(Resource):
    isLeaf = True

    def __init__(self):
        Resource.__init__(self)
        #self.putChild(b"status", Status())
        #self.putChild(b"follow", Follow())
        #self.putChild(b"delay", Delay())
    
    def deferRequest(self, request, delay, f, *a, **kw):
        def _cancelrequest(_):
            # silence CancelledError
            d.addErrback(lambda _: None)
            d.cancel()

        d = deferLater(reactor, delay, f, *a, **kw)
        request.notifyFinish().addErrback(_cancelrequest)
        return d

    def getChild(self, name, request):
        return self
            
    def render_GET(self, request):
        path = "/var/www/html/books.toscrape.com/"
        filepath = '/'.join(request.postpath)
        fname = path + filepath

        '''
        if "delay" in fname:
            n = getarg(request, b"n", 1, type=float)
            b = getarg(request, b"b", 1, type=int)
            if b:
                # send headers now and delay body
                request.write('')
            self.deferRequest(request, n, self._delayedRender, request, n)
            return NOT_DONE_YET
        '''
        n = 1

        self.deferRequest(request, n, self._delayedRender, request, n)    
        return NOT_DONE_YET

        with open(fname) as f:
            s = f.read()
        return s

    def _delayedRender(self, request, n):
        request.write(to_bytes("Response delayed for %0.3f seconds\n" % n))
        print "hi"
        request.finish()    

resource = Home()
factory = Site(resource)
endpoint = endpoints.TCP4ServerEndpoint(reactor, 8880, interface='0.0.0.0')
endpoint.listen(factory)
reactor.run()