https://fedorahosted.org/sssd/ticket/1478
I've tested that the following Python code now works fine:
from SSSDConfig import SSSDConfig
sssdconfig = SSSDConfig()
sssdconfig.import_config('/etc/sssd/sssd.conf')
ldap_domain = sssdconfig.new_domain('autofstest')
ldap_domain.add_provider('ldap', 'autofs')
ldap_domain.set_option('ldap_autofs_map_object_class', 'nisMap')
works fine.