javascript - Django gives TypeError at /loadFcs expected string or buffer

Question

In my js I make a simple request as below

$.post('/loadFcs', function(data) {alert('hi');});

In my urls.py, I have

from views import loadFcs
  urlpatterns = patterns('',
  ('^$', direct_to_template, { 'template': 'index.html' }),
  ('^loadFcs$', loadFcs)
 )

In my views I have

@require_POST
def loadFcs(request):
  results = {}
  //do some calculation and calucalte results, results looks like {"a":["avalue", "bvalue"], "b":["avalue", "bvalue"]}
  return HttpResponse(json.dumps(results),mimetype="application/json")

But I see the following error in my Firebug console under the 'Response' tab

TypeError at /loadFcs expected string or buffer

Request Method: POST

Where am I making a mistake? I also tried just

      return HttpResponse(json.dumps(results))

but did not work either.