Please answer the following question: Information: - The British United Traction produced various diesel multiple units . - A diesel multiple unit or DMU is a multiple-unit train powered by on-board diesel engines. A DMU requires no separate locomotive, as the engines are incorporated into one or more of the carriages. They may also be referred to as a railcar or railmotor, depending on country. Diesel-powered units may be further classified by their transmission type: diesel-electric (DEMU), diesel-mechanical (DMMU) or diesel-hydraulic (DHMU). - A trolleybus (also known as trolley bus, trolley coach, trackless trolley, trackless tram [in early years] or trolley) is an electric bus that draws power from overhead wires (generally suspended from roadside posts) using spring-loaded trolley poles. Two wires and poles are required to complete the electrical circuit. This differs from a tram or streetcar, which normally uses the track as the return path, needing only one wire and one pole (or pantograph). They are also distinct from other kinds of electric buses, which usually rely on batteries. Power is most commonly supplied as 600-volt direct current, but there have been, and are, exceptions. - British United Traction (BUT) was a joint company owned by the Associated Equipment Company and Leyland Motors which produced railway equipment and trolleybuses. It was established in 1946. - AEC was a British vehicle manufacturer which built buses, motorcoaches and lorries from 1912 until 1979. The acronym stood for Associated Equipment Company, but this name was hardly ever used; instead it traded under the AEC and ACLO brands. - Leyland Motors Limited was a British vehicle manufacturer of lorries, buses and trolleybuses. It gave its name to the British Leyland Motor Corporation formed when it merged with British Motor Holdings, later to become British Leyland after being nationalised. British Leyland later changed its name to simply BL, then in 1986 to Rover Group. What entity does 'british united traction dmus' has the relation 'instance of' with?
Answer:
train