import tensorflow as tf

    # Axis 0    - Batch.
    # Axis 1    - Input Frames, 4 frames.
    # Axis 2, 3 - Height & Width.
    # Axis 4    - Channels RGB, 3 colours.
    x = tf.transpose(observations, [0, 2, 3, 1, 4])
    x_shape = common_layers.shape_list(x)
    x = tf.reshape(x, x_shape[:-2] + [-1])
    dropout = getattr(self.hparams, "dropout_ppo", 0.0)
