The problem

Despite being documented, using expand as a filter (i.e. ['group.users']|expand) is flagged as invalid checking the configuration files.

Environment

• Home Assistant Core release with the issue: 0.108.9
• Last working Home Assistant Core release (if known): N/A
• Operating environment (Home Assistant/Supervised/Docker/venv): venv
• Integration causing this issue: template
• Link to integration documentation on our website: https://www.home-assistant.io/docs/configuration/templating/

Problem-relevant configuration.yaml

{%- set enti = (entities.split(',') if entities is string else entities)|map('trim')|list -%}
{{
    enti|expand
    |map(attribute="entity_id")|reject('eq','')
    |unique|sort
    |tojson
}}

Traceback/Error logs

Invalid config for [script]: invalid template (TemplateAssertionError: no filter named 'expand') for dictionary value @…

Additional information