Ansible - Use template lookup in a role to generate a list of IP addresses from a hostgroup

hostgroup_ips.j2

{% if myhostgroup != '' %}
{% for host in groups[myhostgroup] %}
- {{ hostvars[host]["ansible_default_ipv4"]["address"] }}
{% endfor %}
{% endif %}

playbook.yml

---
- hosts: myhosts
  vars:
    hostgroup_ips: '{{ lookup("template", "hostgroup_ips.j2") | from_yaml }}'
  tasks:
    - debug:
        var: '{{ hostgroup_ips|join(",") }}'