old_contents: from __future__ import unicode_literals
  from __future__ import print_function
  from __future__ import division
  from __future__ import absolute_import
  
  
  __version__ = '0.12.0'
  
new_contents: from __future__ import unicode_literals
  from __future__ import print_function
  from __future__ import division
  from __future__ import absolute_import
  
  
  __version__ = '0.13.0a1'
  
subject: increase version to 0.13.0a1