@classproperty
def described_object_field(cls) -> Field:
    for rel in cls.relations.keys():
        if rel.name.startswith('described_'):
            return rel
    raise TypeError(f'{cls} should have a described field.')
@classproperty
def described_object_field(cls) -> Field:
    for rel in cls.relations.keys():
        if rel.name.startswith('described_'):
            return rel
    raise TypeError(f'{cls} should have a described field.')