import tensorflow as tf

                        tf.assign(target, (1 - self.tau) * target + self.tau * source)
                        for target, source in zip(target_params, source_params)
                    ]
                    # Initializing target to match source variables
                    target_init_op = [
                        tf.assign(target, source)
                        for target, source in zip(target_params, source_params)
                    ]

                    # Control flow is used because sess.run otherwise evaluates in nondeterministic order
