How to declare a host in inventory if we have a YAML file?

# Example YAML inventory for Ansible
all:
  hosts:
    web01:
      ansible_host: 192.168.1.10
      user: admin
    db01:
      ansible_host: 192.168.1.20
      user: dbuser
  children:
    webservers:
      hosts:
        web01:
    databases:
      hosts:
        db01:

In the YAML file, hosts are declared under the hosts key within the respective groups (e.g., all, webservers, databases). Each host is represented as a key with nested parameters such as ansible_host (DNS name or IP address) and user (user for connection). Groups are declared under the children key, and their hosts list the hosts belonging to them.