What does the Typed Relation Dedup Formatter do?

Problem/Motivation

In views, I see "Typed Relation Dedup Formatter" is available but I can't find any documentation that explains what that formatter does. Looking at the code I think it deduplicates by by target id, so a person might be listed once.

I experimented with the Islandora Sandbox https://sandbox.islandora.ca/islandora/christmas-inspiration and see the Dedup formatter ensures the target entity is listed once and rel_types are accumulated:

Contributors
Author, Actor: Lucy Maud Montgomery
Storyteller, Abridger: Darcia Douglas

Proposed resolution

Improve code docs and README to describe behaviour of "Typed Relation Dedup Formatter"

Remaining tasks

1. Specific code doc changes
2. README changes