Ansible loop and dict combine

main.yml

- hosts: localhost
  gather_facts: no
  vars:
    # structure from https://docs.ansible.com/ansible/2.5/plugins/inventory/yaml.html
    inventory:
      all: # keys must be unique, i.e. only one 'hosts' per group
          hosts:
              test1:
              test2:
                  var1: value1
          vars:
              group_var1: value2
          children:   # key order does not matter, indentation does
              other_group:
                  children:
                      group_x:
                          hosts:
                              test5
                  vars:
                      g2_var2: value3
                  hosts:
                      test4:
                          ansible_host: 127.0.0.1
              last_group:
                  hosts:
                      test1 # same host as above, additional group membership
                  vars:
                      last_var: MYVALUE

  tasks:
  - include_tasks: var_item.yml
    vars:
      chiave: "{{item.0}}"
      valore: "{{item.1}}"
    loop_control:
      loop_var: "item"
    with_together:
     - ['a', 'b', 'c']
     - [111, 222, 333]

  - debug:
     var: hosts

  - set_fact:
      inventory: "{{ inventory | combine({'all': {'hosts': hosts}}, recursive=True) }}"

  - debug:
      var: inventory

  - copy:
      content: "{{inventory|to_nice_yaml}}"
      dest: ./inventory

var_item.yml

- set_fact:
    hosts: "{{ hosts | default({}) | combine({chiave: valore}) }}"