old_contents: NUM_VERSION = (0, 1, 2)
  VERSION = ".".join(str(nv) for nv in NUM_VERSION)
  __version__ = VERSION
  
new_contents: NUM_VERSION = (0, 1, 3)
  VERSION = ".".join(str(nv) for nv in NUM_VERSION)
  __version__ = VERSION
  
subject: Bump version.