ansible only use one configuration file, not combine all the configuration files

I found that deprecation_warnings=False setted in /etc/ansible/ansible.cfg has no effect when I have ~/.ansible.cfg.

So I check the document, it says

Changes can be made and used in a configuration file which will be searched for in the following order:

• ANSIBLE_CONFIG (environment variable if set)
• ansible.cfg (in the current directory)
• ~/.ansible.cfg (in the home directory)
• /etc/ansible/ansible.cfg

Ansible will process the above list and use the first file found, all others are ignored.