code: def test_invalid_file(self):
      self.assertEqual(metrics.CalculateFileSize("not_a_file.txt"), -1)
  
imports: import os
  from tensorflow.core.framework import summary_pb2
  from tensorflow.core.framework import versions_pb2
  from tensorflow.core.protobuf import fingerprint_pb2
  from tensorflow.python.eager import test
  from tensorflow.python.saved_model.pywrap_saved_model import metrics
label_desc: Use image node_id 11 for calling the MetricsTest obj's underlying member method code with example usage: obj.test_invalid_file() without return types