old_contents: from abc import ABCMeta, abstractmethod
  
  class ModelAbs(object):
  	__metaclass__ = ABCMeta
  	
  	@abstractmethod
  	def model_infer(self, data_ph, model_params):
  		pass
  
  	@abstractmethod
  	def model_loss(self, data_ph, model_params):
  		pass
  
  	@abstractmethod
  	def model_mini(self, loss):
  		pass
  	
  
new_contents: from abc import ABCMeta, abstractmethod
  import tensorflow as tf
  
  class ModelAbs(object):
      __metaclass__ = ABCMeta
  
      @abstractmethod
      def model_infer(self, data_ph, model_params):
          raise NotImplementedError
  
      @abstractmethod
      def model_loss(self, data_ph, model_params):
          raise NotImplementedError
  
      @abstractmethod
      def model_mini(self, loss):
          raise NotImplementedError
      
  
subject: replace tab