code: def test_native_bed_header(self, bed_filename):
      bed_path = test_utils.genomics_core_testdata(bed_filename)
      with bed.BedReader(bed_path) as reader:
          self.assertEqual(reader.header.num_fields, 12)
      with bed.NativeBedReader(bed_path) as native_reader:
          self.assertEqual(native_reader.header.num_fields, 12)
  
file_path: deepvariant/third_party/nucleus/io/bed_test.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from absl.testing import absltest
  from absl.testing import parameterized
  from third_party.nucleus.io import bed
  from third_party.nucleus.io.python import bed_reader
  from third_party.nucleus.protos import bed_pb2
  from third_party.nucleus.testing import test_utils
label_desc: Use image node_id 3 for calling the BedReaderTests obj's underlying member method code with example usage: obj.test_native_bed_header(bed_filename) without return types