code: def test_exists(self):
      self.assertTrue(
          gfile.Exists(
              test_utils.genomics_core_testdata("test_regions.bedgraph")
          )
      )
      self.assertFalse(
          gfile.Exists(
              test_utils.genomics_core_testdata("does_not_exist")
          )
      )
  
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 1 for calling the GfileTest obj's underlying member method code with example usage: obj.test_exists() without return types