class_docstr: Basic tests for the wrapped DeBruijnGraph class.
code: def test_straightforward_region(self):
      ref_reader = fasta.IndexedFastaReader(testdata.CHR20_FASTA)
      bam_reader = sam.SamReader(testdata.CHR20_BAM)
      region = ranges.parse_literal("chr20:10,000,000-10,000,100")
      ref_seq = ref_reader.query(region)
  
      all_reads = list(bam_reader.query(region))
      dbg30 = debruijn_graph.build(
          ref_seq, all_reads, self.single_k_dbg_options(30)
      )
      self.assertIsNotNone(dbg30)
      self.assertEqual([ref_seq], dbg30.candidate_haplotypes())
  
imports: from absl.testing import absltest
  from absl.testing import parameterized
  from third_party.nucleus.io import fasta
  from third_party.nucleus.io import sam
  from third_party.nucleus.testing import test_utils
  from third_party.nucleus.util import ranges
  from deepvariant import testdata
  from deepvariant.protos import realigner_pb2
  from deepvariant.realigner.python import debruijn_graph
label_desc: Use image node_id 8 for calling the DeBruijnGraphWrapTest obj's underlying member method code with example usage: obj.test_straightforward_region() without return types