MongoEngine : ImproperlyConfigured: settings.DATABASES is improperly configured

Getting the following error when executing the following line of command

from django.contrib.sessions.models import Session
session = Session.objects.get(pk=session_key)

Error:

ImproperlyConfigured: settings.DATABASES is improperly configured. Please supply the   ENGINE value. Check settings documentation for more details.

Followed the following steps for the settings.py file http://docs.mongoengine.org/en/latest/django.html

DATABASES = {
'default': {
    'ENGINE' : 'django.db.backends.dummy',
},
 }

SESSION_ENGINE = 'mongoengine.django.sessions'