How to filter Powermax alerts for most recent use Ansible playbook

---
- name: Get alerts for powermax
  hosts: localhost
  connection: local

  vars:
    unispherehost: "10.x.x.x"
    universion: "100"
    verifycert: False
    user: "smc"
    password: "securePassword123#"
    serial_no: "000120001234"
    days_back: 7

  collections:
    - dellemc.powermax

  tasks:
    - name: Get alerts for powermax
      dellemc.powermax.info:
        unispherehost: "{{unispherehost}}"
        serial_no:  "{{serial_no}}"
        universion: "{{universion}}"
        verifycert: "{{verifycert}}"
        user: "{{user}}"
        password: "{{password}}"
        gather_subset:
          - health
          - alert
    - name: Filter alerts for the last 7 days
      set_fact:
        filtered_alerts: "{{ alert_output.powermax_info.alert | rejectattr('timestamp', 'lt', days_back*24*3600) | list }}"

    - name: Display filtered alerts
      debug:
        var: filtered_alerts

fatal: [localhost]: FAILED! => {
"msg": "The task includes an option with an undefined variable. The error was: 'dict object' has no attribute 'alert'. 'dict object' has no attribute 'alert'\n\nThe error appears to be in '/home/jchang/.ansible/playbooks/powermax_get_health_alert_xdays_be.yml'