Did you know that you can get Ansible module's documentation with ansible-doc?

$ ansible-doc --help
Usage: ansible-doc [options] [module...]

  -h, --help            show this help message and exit
  -l, --list            List available modules
  -M MODULE_PATH, --module-path=MODULE_PATH
                        specify path(s) to module library
  -s, --snippet         Show playbook snippet for specified module(s)
  -v, --verbose         verbose mode (-vvv for more, -vvvv to enable
                        connection debugging)
  --version             show program's version number and exit

So to get help on lineinfile, call ansible-doc lineinfile.