code: def test_genotype_from_matched_truth_none_variant_raises(self):
      with self.assertRaisesRegex(ValueError, "variant cannot be None"):
          variant_labeler._genotype_from_matched_truth(None, self.snp)
  
file_path: deepvariant/deepvariant/labeler/variant_labeler_test.py
imports: from absl.testing import absltest
  from absl.testing import parameterized
  from third_party.nucleus.io import vcf
  from third_party.nucleus.testing import test_utils
  from third_party.nucleus.util import ranges
  from deepvariant import testdata
  from deepvariant.labeler import variant_labeler
label_desc: Use image node_id 6 for calling the VariantLabelerTest obj's underlying member method code with example usage: obj.test_genotype_from_matched_truth_none_variant_raises() without return types