i am trying to write an extra line into my /etc/ansible/hosts file using an ansible playbook. Sadly I can not find an regex that matches my problem.

Here is my /etc/ansible/hosts file (example):

all:
  hosts:
    localhost:
      ansible_user: admin
  children:
    ABC:
      children:
        abc_D1:
          hosts:
        abc_D2:
          hosts:
    DAC:
      children:

I am trying to add and new line here:

all:
  hosts:
    localhost:
      ansible_user: admin
  children:
    ABC:
      children:
        abc_D1:
          hosts:
            **THIS IS MY NEW LINE**
        abc_D2:
          hosts:
    DAC:
      children:

I can not figure out what kind of regular expression I need. This is my current playbook:

 name: Insert comment in YAML file
  hosts: localhost
  connection: local
  vars:
    inventory_file: /etc/ansible/hosts
  tasks:
    - name: Ensure hosts section exists under abc_D1
      lineinfile:
        path: "{{ inventory_file }}"
        line: "          hosts:"
        insertafter: '        abc_D1:'
    - name: Insert new Host
      lineinfile:
        path: "{{ inventory_file }}"
        line: "THIS IS MY NEW LINE"
        insertafter: $'        abc_D1:n          hosts:'

my regex from insertafter is working when used in cat /etc/ansible/hosts | grep $’ abc_D1:n hosts:’ , but not in my ansible playbook.

Any ideas?