old_contents: """Collection of functionality mix-ins.
  
  This module contains standalone classes that can be safely mixed
  into the :class:`~test_helpers.bases.BaseTest` class.  Each mixin
  extends the functionality of the test case by adding behaviors,
  methods, and attributes - for example, patching well-understood
  functionality or automatically creating/destroying an in memory
  UDP server.
  
  When creating a mixin it is important to take not that you
  should strive to keep the Method Resolution Order (MRO) as clean
  as possible.  Each mixin class should ideally only inherit from
  ``object``.
  
  """
  
  from .patch_mixin import PatchMixin
  
  __all__ = ('PatchMixin')
  
new_contents: """Collection of functionality mix-ins.
  
  This module contains standalone classes that can be safely mixed
  into the :class:`~test_helpers.bases.BaseTest` class.  Each mixin
  extends the functionality of the test case by adding behaviors,
  methods, and attributes - for example, patching well-understood
  functionality or automatically creating/destroying an in memory
  UDP server.
  
  When creating a mixin it is important to take not that you
  should strive to keep the Method Resolution Order (MRO) as clean
  as possible.  Each mixin class should ideally only inherit from
  ``object``.
  
  """
  
  from .patch_mixin import PatchMixin
  
  __all__ = ('PatchMixin',)
  
subject: Fix __all__.