code: def tf_loss_per_instance(self, states, internals, actions, terminal, reward,
                               next_states, next_internals, update, reference=None):
          
          raise NotImplementedError
docs: Creates the TensorFlow operations for calculating the loss per batch instance.
  
          Args:
              states: Dict of state tensors.
              internals: Dict of prior internal state tensors.
              actions: Dict of action tensors.
              terminal: Terminal boolean tensor.
              reward: Reward tensor.
              next_states: Dict of successor state tensors.
              next_internals: List of posterior internal state tensors.
              update: Boolean tensor indicating whether this call happens during an update.
              reference: Optional reference tensor(s), in case of a comparative loss.
  
          Returns:
              Loss per instance tensor.