code: def test_write_raises_with_unknown_contig(self):
      with self.assertRaisesRegexp(ValueError, _UNKNOWN_CONTIG_ERROR):
          self.variant.reference_name = "BadChrom"
          self.writer.write(self.variant)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import copy
  from absl.testing import absltest
  from absl.testing import parameterized
  from etils import epath
  from third_party.nucleus.io import tfrecord
  from third_party.nucleus.io import vcf
  from third_party.nucleus.io.python import vcf_writer
  from third_party.nucleus.protos import reference_pb2
  from third_party.nucleus.protos import variants_pb2
  from third_party.nucleus.testing import test_utils
label_desc: Use image node_id 4 for calling the WrapVcfWriterTest obj's underlying member method code with example usage: obj.test_write_raises_with_unknown_contig() without return types