Whoops, forgot we already use json prefix
json output: separate mechanism to filter Persons
json: more semantic machinery (named lines)

We introduce the notion of named lines (lines with prefixes)
and some helpers for working with them <named foo...>

The prefixes identify the lines, which can be useful if you
know which line you want to do something with.

The utilities do things like picking lines out or modifying
a single line in a block of lines

It's a bit like the rewrite function in the brat code