The '--extra' argument of 'puppet facts find' lacks documentation

I am trying to use the command:

puppet facts find

As is, it returns all the facts.

I am trying to use the '–extra' parameter.

puppet facts find –extra HASH

But I cannot manage to make it work:

# puppet facts find --extra '{ "value" => [ "ssh" ] }'

Error: Could not call 'find' on 'facts': undefined method `inject' for "{ \"value\" => [ \"ssh\" ] }":String

Did you mean? inspect

Error: Could not call 'find' on 'facts': undefined method `inject' for "{ \"value\" => [ \"ssh\" ] }":String

Did you mean? inspect

Error: Try 'puppet help facts find' for usage

The documentation is here: https://puppet.com/docs/puppet/latest/man/facts.html

It states this argument take a HASH as argument without precising the format.

There is no example showing how to use this '–extra' argument.

I think that the documentation should be clearer on the format expected for the '–extra' argument and an example showing how to use it would be a welcome addition.