Does merge.dev list enumerated values anywhere?

Question isn't specifically about this client but not sure where to ask dev questions about merge.dev.

I want to include a linkedin url for a candidate and I'm not seeing which values are allowed for `url_type`. If I look at data I see 'LinkedIn' as a raw_value but the value is MERGE_NONSTANDARD_VALUE. Assume that means I can read and not set it.