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##### SUMMARY
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https://docs.ansible.com/ansible/latest/collections/ansible/builtin/password_lookup.html :

> Define comma separated list of names that compose a custom character set in the generated passwords.
> They can be either parts of Python's string module attributes (ascii_letters,digits, etc) or are used literally ( :, -).

I suggest to list all possible names or at least add a link to python string module documentation: https://docs.python.org/3/library/string.html

Now you have to search for the relevant python documentation yourself.

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##### ISSUE TYPE
- Documentation Report

##### COMPONENT NAME
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ansible.builtin.password

##### ADDITIONAL INFORMATION
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notes:
      - A great alternative to the password lookup plugin,
        if you don't need to generate random passwords on a per-host basis,
        would be to use Vault in playbooks.
        Read the documentation there and consider using it first,
        it will be more desirable for most applications.
      - If the file already exists, no data will be written to it.
        If the file has contents, those contents will be read in as the password.
        Empty files cause the password to return as an empty string.
      - 'As all lookups, this runs on the Ansible host as the user running the playbook, and "become" does not apply,
        the target file must be readable by the playbook user, or, if it does not exist,
        the playbook user must have sufficient privileges to create it.
        (So, for example, attempts to write into areas such as /etc will fail unless the entire playbook is being run as root).'
"""
EXAMPLES = """
- name: create a mysql user with a random password
  mysql_user:
    name: "{{ client }}"
    password: "{{ lookup('password', 'credentials/' + client + '/' + tier + '/' + role + '/mysqlpassword length=15') }}"
    priv: "{{ client }}_{{ tier }}_{{ role }}.*:ALL"
- name: create a mysql user with a random password using only ascii letters
  mysql_user:
    name: "{{ client }}"
    password: "{{ lookup('password', '/tmp/passwordfile chars=ascii_letters') }}"
    priv: '{{ client }}_{{ tier }}_{{ role }}.*:ALL'
- name: create a mysql user with an 8 character random password using only digits
  mysql_user:
    name: "{{ client }}"
    password: "{{ lookup('password', '/tmp/passwordfile length=8 chars=digits') }}"
    priv: "{{ client }}_{{ tier }}_{{ role }}.*:ALL"