-record(l4u_obj, {
    name :: binary(),
    pid :: l4u@sys_bridge:pid_(),
    get_env :: fun(() -> l4u@l4u_type:env()),
    eval :: fun((list(l4u@l4u_type:expr())) -> {ok, l4u@l4u_type:expr()} |
        {error, binary()}),
    read :: fun((binary()) -> {ok, list(l4u@l4u_type:expr())} |
        {error, binary()}),
    print :: fun((l4u@l4u_type:expr()) -> binary())
}).