
  [;1m-spec relation(Tuples) -> Relation[0m
  [;1m                  when Relation :: relation(), Tuples :: [tuple()].[0m

  Equivalent to [;;4mrelation(Tuples, Type)[0m where [;;4mType[0m is the size of
  the first tuple of [;;4mTuples[0m is used if there is such a tuple.

  If tuples is [;;4m[][0m, then [;;4mType[0m is [;;4m2[0m.
