code: def test_flatten(self):
      self.assertEqual([1, 2, 3, 4], flatten(self.a_list))
  
file_path: tcav/tcav/utils_test.py
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from tensorflow.python.platform import googletest
  from tcav.tcav_results.results_pb2 import Result, Results
  from tcav.utils import flatten, process_what_to_run_expand, process_what_to_run_concepts, process_what_to_run_randoms, results_to_proto
label_desc: Use image node_id 2 for calling the UtilsTest obj's underlying member method code with example usage: obj.test_flatten() without return types