[keycloak-user] Apply group membership filter on ldap login

I am using keycloak 1.6.1.Final with Active Directory/LDAP. I am have not seen any examples of authenticating users within a group membership (memberOf). I also looked at the tests but no luck. Any help will be appreciated. I just need to be able to set up a user federation using ldap/AD and restrict only to users of a certain group. Thanks.