code: def test_reading(self):
      with gfile.Open(
          test_utils.genomics_core_testdata("headerless.sam")
      ) as f:
          for line in f:
              self.assertTrue(line.startswith("SRR3656745"))
  
file_path: deepvariant/third_party/nucleus/io/gfile_test.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from absl.testing import absltest
  from third_party.nucleus.io import gfile
  from third_party.nucleus.testing import test_utils
label_desc: Use image node_id 3 for calling the GfileTest obj's underlying member method code with example usage: obj.test_reading() without return types