code: def _rollout_metadata(batch_env):
    
    batch_env_shape = batch_env.observ.get_shape().as_list()
    batch_size = [batch_env_shape[0]]
    shapes_types_names = [
        # TODO(piotrmilos): possibly retrieve the observation type for batch_env
        (batch_size + batch_env_shape[1:], batch_env.observ_dtype, "observation"),
        (batch_size, tf.float32, "reward"),
        (batch_size, tf.bool, "done"),
        (batch_size + list(batch_env.action_shape), batch_env.action_dtype,
         "action"),
        (batch_size, tf.float32, "pdf"),
        (batch_size, tf.float32, "value_function"),
    ]
    return shapes_types_names
docs: Metadata for rollouts.