old_contents: # flake8: noqa
  from dataclasses_json.api import (DataClassJsonMixin,
                                    LetterCase,
                                    dataclass_json)
  from dataclasses_json.cfg import config, global_config, Exclude
  from dataclasses_json.undefined import CatchAll, Undefined
  
new_contents: # flake8: noqa
  from dataclasses_json.api import (DataClassJsonMixin,
                                    LetterCase,
                                    dataclass_json)
  from dataclasses_json.cfg import config, global_config, Exclude
  from dataclasses_json.undefined import CatchAll, Undefined
  
  __all__ = ['DataClassJsonMixin', 'LetterCase', 'dataclass_json',
             'config', 'global_config', 'Exclude',
             'CatchAll', 'Undefined']
  
subject: Update __init__.py (#291)