def test_rel_cast(): knows = Rel("KNOWS", since=1999) assert Rel.cast() == Rel() assert Rel.cast(None) is None assert Rel.cast(knows) is knows assert Rel.cast("KNOWS") == Rel("KNOWS") assert Rel.cast(since=1999) == Rel(since=1999) assert Rel.cast("KNOWS", since=1999) == Rel("KNOWS", since=1999) assert Rel.cast({"since": 1999}) == Rel(since=1999) assert Rel.cast(("KNOWS", {"since": 1999})) == knows assert Rel.cast(Relationship({}, "KNOWS", {})) == Rel("KNOWS")