How to use to_url function?

[hunter]

Can anyone share an example of using the to_url function in pipeline rule? I’m trying the following variations

debug(to_url(url:www.yahoo.com));

debug(to_url(url:“www.yahoo.com”));

debug(to_url(“www.yahoo.com”));

but I get this error in the log

2018-08-24T17:45:54.723+10:00 INFO [Function] PIPELINE DEBUG: Passed value is NULL.

[jan (Jan Doberstein)]

look at this test how it should run: https://github.com/Graylog2/graylog-plugin-pipeline-processor/blob/master/plugin/src/test/resources/org/graylog/plugins/pipelineprocessor/functions/urls.txt

[hunter]

so, the to_url() return an object. Why this wasn’t mentioned in the documentation … how can we explore all the possible fields of such objects?