title: How to colonize Ansible inventories in yaml format
body: <p>I got this task to convert Ansible inventories from ini to yml, so I take the working ini file and make the usual rounds:
  - Github: check - solution hangs
  - Online tool: check - solution does not resemble anything from this planet
  - Last resort: I read <a href="https://docs.ansible.com/ansible/latest/plugins/inventory/yaml.html" rel="nofollow noreferrer">the official guide</a> that brings the following example:</p>
  
  <pre><code>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
  </code></pre>
  
  <p>Cool, I quickly turn my original ini to this beauty</p>
  
  <p>ORIGINAL</p>
  
  <pre><code>[thingiebob_master]
  thng-esxi96
  
  [thingiebob_slaves]
  thng-esxi97
  </code></pre>
  
  <p>CONVERTED v1</p>
  
  <pre><code>all:
     children:
          thingiebob_master:
              hosts: thng-esxi96
          thingiebob_slaves:
              hosts:
                  thng-esxi97
  </code></pre>
  
  <p>I can run a ping and it reaches both machines. But when I add another node to the second group:
  CONVERTED v2</p>
  
  <pre><code>all:
     children:
          thingiebob_master:
              hosts: thng-esxi96
          thingiebob_slaves:
              hosts:
                  thng-esxi97
                  thng-esxi98
  </code></pre>
  
  <p>I get an error:</p>
  
  <pre><code>PLAY [all] **************************************************************************************
  
  TASK [Gathering Facts] **************************************************************************
  fatal: [thng-esxi97 thng-esxi98]: UNREACHABLE! =&gt; {"changed": false, "msg": "Failed to connect to the host via ssh: ssh: 
  Could not resolve hostname thng-esxi97 thng-esxi98: Name or service not known\r\n", "unreachable": true}
  </code></pre>
  
  <p>But if I put a colon after them, effectively turning them into keys, as in v3 below, all three nodes are found and pinged.
  CONVERTED v3</p>
  
  <pre><code>    all:
         children:
              thingiebob_master:
                  hosts: thng-esxi96
              thingiebob_slaves:
                  hosts:
                      thng-esxi97:
                      thng-esxi98:
  </code></pre>
  
  <p>Result</p>
  
  <pre><code>PLAY [all] **************************************************************************************
  
  TASK [Gathering Facts] **************************************************************************
  ok: [thng-esxi98]
  ok: [thng-esxi96]
  ok: [thng-esxi97]
  
  TASK [ping] *************************************************************************************
  ok: [thng-esxi97]
  ok: [thng-esxi96]
  ok: [thng-esxi98]
  
  PLAY RECAP **************************************************************************************
  thng-esxi96               : ok=2    changed=0    unreachable=0    failed=0
  thng-esxi97               : ok=2    changed=0    unreachable=0    failed=0
  thng-esxi98               : ok=2    changed=0    unreachable=0    failed=0
  </code></pre>
  
  <p>Question: (How) Can I add multiple nodes to my thingiebob_slaves group? (Without colonizing them.)</p>