Make children group

howto make children group like in ansible?
I try with this one but didn’t work

routers_iosxr:
    username: user
    password: pass
    platform: ios
    port: 22
    children:
        - ASR9xx
        - 12xxx
    connection_options:
        netmiko:
            platform: cisco_ios

Hello,
I’d suggest you to read the following tutorial:

https://nornir.readthedocs.io/en/latest/tutorials/intro/inventory.html