Gets a handle of the engine executing the call. This handle can be used like the handles returned from engine_create/2, i.e. all operations that are defined for engine handles. Note that holding a reference to an engine can prevent it from being garbage collected.
    ?- engine_self(E), get_engine_property(E, status, S).
    E = $&(engine,"5ce9")
    S = running
    Yes (0.00s cpu)