How do I edit the authentication.py to configure LDAP?

I am in the process of editing the authentication.py file following the LDAP part 2 instructions. I just need some clarification on how to do this exactly. Will simply replacing the contents of the file, allow LDAP auth to start working if I have python-ldap already installed?

Here is the current file/path:

/opt/questions/qa/apps/osqa/forum_modules/localauth$

from forum.authentication.base import AuthenticationConsumer, ConsumerTemplateContext, InvalidAuthentication
from forms import ClassicLoginForm

class LocalAuthConsumer(AuthenticationConsumer):
    def process_authentication_request(self, request):
        form_auth = ClassicLoginForm(request.POST)

        if form_auth.is_valid():
            return form_auth.get_user()
        else:
            raise InvalidAuthentication(" ".join(form_auth.errors.values()[0]))

class LocalAuthContext(ConsumerTemplateContext):
    mode = 'STACK_ITEM'
    weight = 1000
    human_name = 'Local authentication'
    stack_item_template = 'modules/localauth/loginform.html'
    show_to_logged_in_user = False

What is suggested on the DLAP part 2 page (where I am a bit confused).

import ldap
from forum.authentication.base import  AuthenticationConsumer, InvalidAuthentication, ConsumerTemplateContext
from forms import ClassicLoginForm
from forum.models import User

# ACTIVE DIRECTORY SETTINGS
AD_DNS_NAME = 'domain.net'
AD_LDAP_URL = 'ldap://%s' % (AD_DNS_NAME) #no port specified, default port use

class LocalAuthConsumer(AuthenticationConsumer):
    def process_authentication_request(self, request):
        try:
            # Autenticate user in LDAP
            con = ldap.initialize(AD_LDAP_URL)
            username = request.POST.get('username', None)
            password = request.POST.get('password', None)
            base_dn = 'ou=All Users,dc=domain,dc=com,dc=au'
            filter = '(sAMAccountName=' + username + ')'
            attrs = ['mail']
            if not (username and password):
                raise InvalidAuthentication("Invalid data")
            dn = '%s@%s' % (username, AD_DNS_NAME)
            #careful there might be a bug here use regex to filter special chars
            #ldap behaves wierd with special chars
            con.simple_bind_s(dn, password)
            mailsearch = con.search_s(base_dn, ldap.SCOPE_SUBTREE, filter, attrs )[0][1]
            emailaddress = mailsearch['mail'][0]
            con.unbind_s()
            try:# If user is in datatbase carry on
                user = User.objects.get(username=username)
            except User.DoesNotExist:# not in the database add user to database
                user =  User(username=username, email=emailaddress)
                user.set_unusable_password()
                user.save()
            return user
        # Case the user is not authentic or something goes wrong
        except ldap.NO_SUCH_OBJECT, e:
            con.unbind_s()
            raise InvalidAuthentication("The user does not exist")
        except ldap.INVALID_CREDENTIALS, e:
            con.unbind_s()
            raise InvalidAuthentication("Invalid username or password")
        except ldap.LDAPError, e:
            con.unbind_s()
            raise InvalidAuthentication("LDAP error")

class LocalAuthContext(ConsumerTemplateContext):
    mode = 'STACK_ITEM'
    weight = 1000
    human_name = 'AD authentication'
    stack_item_template = 'modules/localauth/loginform.html'
    show_to_logged_in_user = False