code: def test_get_ref_haplotype_and_offset(
      self,
      dv_variant,
      cohort_variants,
      expected_ref_haplotype,
      expected_ref_offset,
  ):
      ref_reader = fasta.IndexedFastaReader(testdata.GRCH38_FASTA)
      (
          ref_haplotype,
          ref_offset,
      ) = allele_frequency.get_ref_haplotype_and_offset(
          dv_variant, cohort_variants, ref_reader
      )
      self.assertEqual(ref_haplotype, expected_ref_haplotype)
      self.assertEqual(ref_offset, expected_ref_offset)
  
file_path: deepvariant/deepvariant/allele_frequency_test.py
imports: from absl.testing import absltest
  from absl.testing import parameterized
  from third_party.nucleus.io import fasta
  from third_party.nucleus.io import vcf
  from third_party.nucleus.protos import variants_pb2
  from deepvariant import allele_frequency
  from deepvariant import testdata
  from deepvariant.protos import deepvariant_pb2
label_desc: Use image node_id 2 for calling the AlleleFrequencyTest obj's underlying member method code with example usage: obj.test_get_ref_haplotype_and_offset(dv_variant, cohort_variants, expected_ref_haplotype, expected_ref_offset) without return types