
[;1m  from_sets/1[0m

  Returns the unordered set containing the sets of list [;;4mListOfSets[0m.

    1> S1 = sofs:relation([{a,1},{b,2}]),
    S2 = sofs:relation([{x,3},{y,4}]),
    S = sofs:from_sets([S1,S2]),
    sofs:to_external(S).
    [[{a,1},{b,2}],[{x,3},{y,4}]]

  Returns the ordered set containing the sets of the non-empty tuple [;;4m[0m
  [;;4mTupleOfSets[0m.
