!7

p-exp {
  assertSize(4, pnl(asList(allCombinations(ll(ll("a", "b"), ll("c"), ll("d", "e"))))));
  assertEqualsVerbose(ll(ll()), asList(allCombinations(ll())));
  assertEqualsVerbose(ll(), asList(allCombinations(ll(ll(), ll("a")))));
}