def validate(cls, trecs, tr, errata):
        print(Counter(_[1] for _ in trecs).most_common()[:5])
        ('CxA1', 2), ('Tu1', 2), ('LOT1', 2), ('ECIC3', 2)
        assert len(tr) == len(trecs), 'Abbreviations in tr are not unique!'
        return tr, errata