code: def test_waiting_backoff():
      conf = retry.RetryConf().waiting(1, backoff=2)
      with erroneous_runner(DUMMY_RUN) as run:
  
          @retry.retry(conf)
          def foo():
              run()
  
      foo()
  
imports: import contextlib
  import datetime
  import pytest
  import library.python.retry
label_desc: Use image node_id 18 for calling a global function with example usage: test_waiting_backoff() without return types