old_contents: from .exposure import histogram, equalize, equalize_hist, \
                        rescale_intensity, cumulative_distribution
  from ._adapthist import equalize_adapthist
  
new_contents: from .exposure import histogram, equalize, equalize_hist, \
                        rescale_intensity, cumulative_distribution
  from ._adapthist import equalize_adapthist
  
  __all__ = ['histogram',
             'equalize',
             'equalize_hist',
             'equalize_adapthist',
             'rescale_intensity',
             'cumulative_distribution']
  
subject: Add __all__ to exposure package