How to use the kipoiseq.dataclasses.Variant.from_cyvcf function in kipoiseq

def test_extract(variant_seq_extractor):
    variants = [Variant.from_cyvcf(v) for v in VCF(vcf_file)]

    interval = Interval('chr1', 2, 9)

    seq = variant_seq_extractor.extract(interval, variants, anchor=5)
    assert len(seq) == interval.end - interval.start
    assert seq == 'CGAACGT'

    interval = Interval('chr1', 2, 9, strand='-')
    seq = variant_seq_extractor.extract(interval, variants, anchor=5)
    assert len(seq) == interval.end - interval.start
    assert seq == 'ACGTTCG'

    interval = Interval('chr1', 4, 14)
    seq = variant_seq_extractor.extract(interval, variants, anchor=7)
    assert len(seq) == interval.end - interval.start
    assert seq == 'AACGTAACGT'

with pytest.raises(AttributeError):
        v.alt = 'asd'

    # non-fixed arguments
    v.id = 'asd'
    v.qual = 10
    v.filter = 'asd'
    v.source = 2

    assert isinstance(Variant("chr1", '10', 'C', 'T').pos, int)

    # from cyvcf2
    vcf = cyvcf2.VCF('tests/data/test.vcf.gz')
    cv = list(vcf)[0]

    v2 = Variant.from_cyvcf(cv)
    assert isinstance(v2.source, cyvcf2.Variant)

def __next__(self):
        return Variant.from_cyvcf(super().__next__())