Helper functions for the Relation, which never change a given relation and share its sets, so do not change them either.
Readonly
Relates every key to values, which all of them share.
values
All pairs of all relations, in one pass, and the relation itself if it is the only one holding any.
The relation without the keys other holds, itself if there are none.
other
Relation.fromPairs([['x', 1], ['x', 2]]); // x relates to 1 and 2 Copy
Relation.fromPairs([['x', 1], ['x', 2]]); // x relates to 1 and 2
Helper functions for the Relation, which never change a given relation and share its sets, so do not change them either.