Extending get_url module with 'backup' parameter

I miss the ‘backup’ parameter in the ‘get_url’ (working in the same manner as ‘backup’ in the ‘copy’ module) so I wanted to extend the module myself.

I checked the code of get_url.py and copy.py and before changing I added:

`
backup=yes

`

to the playbook. To my surprise playbook did not fail. If I changed the parameter name to something other it stopped with:

`
msg: unsupported parameter for module: backupdest

`

What am I missing? Is there some “global” check for parameters outside of individual modules?