old_contents: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  
  class VariationalStrategy(object):
      def __init__(self, variational_dist, prior_dist):
          self.variational_dist = variational_dist
          self.prior_dist = prior_dist
  
      def kl_divergence(self):
          raise NotImplementedError
  
new_contents: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  
  
  class VariationalStrategy(object):
      def __init__(self, variational_dist, prior_dist):
          self.variational_dist = variational_dist
          self.prior_dist = prior_dist
  
      def kl_divergence(self):
          raise NotImplementedError
  
subject: Fix variational_strategy.py lint