old_contents: # Functions, classes and constants exported here will be available
  # when the `example` module is imported.
  
  __all__ = ['A', 'B']
  
  from .code import A, B
  
new_contents: # Functions, classes and constants exported here will be available
  # when the `example` module is imported.
  from .code import A, B
  
  __all__ = ['A', 'B']
  
subject: fix flake8 error in master