---
- name: Adding user and self practice of automating an automation
  hosts: nodes
  vars_files: /tmp/list.yml
  tasks:
    - name: Real work account adding
      user:
        name: "{{ item }}"
        state: present
      with_items: "{{ username }}"
...
# we use hash value loop only when there is key with multiple value and one is dependent on other key.