import tensorflow as tf

            # Use fixed archs if specified, otherwise use placeholders'
            (normal_arch, reduction_arch) = self._get_fixed_cell_archs(**knobs)
            normal_arch = normal_arch if not use_dynamic_arch else ph.normal_arch
            reduction_arch = reduction_arch if not use_dynamic_arch else ph.reduction_arch

            # Initialize steps variable
            step = self._make_var('step', (), dtype=tf.int32, trainable=False, initializer=tf.initializers.constant(0))

            # For train dataset, preprocess & do inference
            utils.logger.log('Building model for training...')
            (train_X, train_classes, train_dataset_init_op) = \
                self._preprocess(ph.train_images, ph.train_classes, is_train=True, **knobs)
