code: def testDumpSizeBytesIsNoneForNonexistentFilePath(self):
      dump_root = "/tmp/tfdbg_1"
      debug_dump_rel_path = (
          "ns1/ns2/node_foo_1_2_DebugIdentity_1472563253536385"
      )
      datum = debug_data.DebugTensorDatum(
          dump_root, debug_dump_rel_path
      )
  
      self.assertIsNone(datum.dump_size_bytes)
  
imports: import os
  import platform
  import tempfile
  import numpy
  from tensorflow.core.framework import graph_pb2
  from tensorflow.core.framework import tensor_pb2
  from tensorflow.python.debug.lib import debug_data
  from tensorflow.python.framework import test_util
  from tensorflow.python.lib.io import file_io
  from tensorflow.python.platform import gfile
  from tensorflow.python.platform import googletest
  from tensorflow.python.platform import test
label_desc: Use image node_id 2 for calling the DebugTensorDatumTest obj's underlying member method code with example usage: obj.testDumpSizeBytesIsNoneForNonexistentFilePath() without return types