code: def learn(self, grad_arr, fix_opt_flag=False):
          '''
          Update this Discriminator by ascending its stochastic gradient.
  
          Args:
              grad_arr:       `np.ndarray` of gradients.
              fix_opt_flag:   If `False`, no optimization in this model will be done.
          
          Returns:
              `np.ndarray` of delta or gradients.
          '''
          deconvolution_layer_list = self.__deconvolution_layer_list[::-1]
          for i in range(len(deconvolution_layer_list)):
              try:
                  grad_arr = deconvolution_layer_list[i].back_propagate(grad_arr)
              except:
                  self.__logger.debug("Error raised in Convolution layer " + str(i + 1))
                  raise
  
          if fix_opt_flag is False:
              self.__optimize(self.__learning_rate, 1)
          
          return grad_arf learn(self, grad_arr, fix_opt_flag=False):
          '''
          Update this Discriminator by ascending its stochastic gradient.
  
          Args:
              grad_arr:       `np.ndarray` of gradients.
              fix_opt_flag:   If `False`, no optimization in this model will be done.
          
          Returns:
              `np.ndarray` of delta or gradients.
          '''
          deconvolution_layer_list = self.__deconvolution_layer_list[::-1]
          for i in range(len(deconvolution_layer_list)):
              try:
                  grad_arr = deconvolution_layer_list[i].back_propagate(grad_arr)
              except:
                  self.__logger.debug("Error raised in Convolution layer " + str(i + 1))
                  raise
  
          if fix_opt_flag is False:
              self.__optimize(self.__learning_rate, 1)
          
          return grad_arr
docs: Update this Discriminator by ascending its stochastic gradient.
  
          Args:
              grad_arr:       `np.ndarray` of gradients.
              fix_opt_flag:   If `False`, no optimization in this model will be done.
          
          Returns:
              `np.ndarray` of delta or gradients.