old_contents: 
  VERSION = (0, 5, 0)
  
  
  # NOTE: This method was removed in 0.4.0, but restored in 0.4.2 after use-cases were
  # reported that were impossible by merely subclassing MPTTModel.
  def register(*args, **kwargs):
      """
      Registers a model class as an MPTTModel, adding MPTT fields and adding MPTTModel to __bases__.
      This is equivalent to just subclassing MPTTModel, but works for an already-created model.
      """
      from mptt.models import MPTTModelBase
      return MPTTModelBase.register(*args, **kwargs)
  
  
  # Also removed in 0.4.0 but restored in 0.4.2, otherwise this 0.3-compatibility code will break:
  #     if hasattr(mptt, 'register'):
  #         try:
  #             mptt.register(...)
  #         except mptt.AlreadyRegistered:
  #             pass
  
  class AlreadyRegistered(Exception):
      "Deprecated - don't use this anymore. It's never thrown, you don't need to catch it"
  
new_contents: 
  VERSION = (0, 5, '+dev')
  
  
  # NOTE: This method was removed in 0.4.0, but restored in 0.4.2 after use-cases were
  # reported that were impossible by merely subclassing MPTTModel.
  def register(*args, **kwargs):
      """
      Registers a model class as an MPTTModel, adding MPTT fields and adding MPTTModel to __bases__.
      This is equivalent to just subclassing MPTTModel, but works for an already-created model.
      """
      from mptt.models import MPTTModelBase
      return MPTTModelBase.register(*args, **kwargs)
  
  
  # Also removed in 0.4.0 but restored in 0.4.2, otherwise this 0.3-compatibility code will break:
  #     if hasattr(mptt, 'register'):
  #         try:
  #             mptt.register(...)
  #         except mptt.AlreadyRegistered:
  #             pass
  
  class AlreadyRegistered(Exception):
      "Deprecated - don't use this anymore. It's never thrown, you don't need to catch it"
  
subject: bump version to 0.5.+dev. 'pre' never made much sense to me. at least 0.5.+dev > 0.5.0 :)