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%% SPDX-License-Identifier: Apache-2.0
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[;1m  relation(Tuples)[0m

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

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

[;1mExamples[0m

    1> S1 = sofs:relation([{1,a},{1,b},{1,a}]).
    2> sofs:to_external(S1).
    [{1,a},{1,b}]
    3> sofs:type(S1).
    [{atom,atom}]
    4> sofs:type(sofs:relation([])).
    [{atom,atom}]
    5> sofs:type(sofs:relation([], 3)).
    [{atom,atom,atom}]
    6> sofs:relation([a,b,c]).
    ** exception error: bad argument
         in function  sofs:relation/1
