Question: What flag does the Swiss born Formula One driver who competed in the 2015 season for Lotus race under?

Context paragraphs:
Lotus E23 Hybrid: The Lotus E23 Hybrid is a Formula One racing car which Lotus used to compete in the 2015 Formula One season.  It was driven by Romain Grosjean and Pastor Maldonado.  This was the team's only car to use Mercedes engines, after a 20-year partnership with Renault.  The E23 Hybrid was also the first Enstone-based car to be powered by other than a Renault engine since the Ford-powered Benetton B194 in .

Lotus 16: The Lotus 16 was the second single-seat racing car designed by Colin Chapman, and was built by his Lotus Cars manufacturing company for the Team Lotus racing squad.  The Lotus 16 was constructed to compete in both the Formula One and Formula Two categories, and was the first Lotus car to be constructed for Formula One competition.  Its design carried over many technological features of the first Lotus single-seater, the Lotus 12, as well as incorporating ideas which Chapman had been developing while working on the Vanwall racing cars.  Indeed, such was the visual similarity between the Vanwall and Lotus 16 designs that the Lotus was often dubbed the ""mini Vanwall"" by the contemporary motor sport press.  Although the Lotus 16 only scored five Formula One World Championship points in the three seasons during which it was used, its raw pace pointed the way for its more successful successors, the Lotus 18 and 21.

Superleague Formula round Germany: The Superleague Formula round Germany is a round of the Superleague Formula.  In the 2008 edition at the Nürburgring, ex Formula One driver Robert Doornbos took his first Superleague Formula win, also taking A.C. Milan's first race victory.  It was also the round where another Formula One driver Antônio Pizzonia made his Superleague Formula debut.  In the events only other race, GP2 Series driver Yelmer Buurman took his and PSV Eindhovens first victory in Superleague Formula.

Lotus F1: Lotus F1 Team was a British Formula One racing team.  The team competed under the Lotus name from 2012 until 2015, following the renaming of the former Renault team based at Enstone in Oxfordshire.  The Lotus F1 Team was majority owned by Genii Capital.  Lotus F1 was named after its branding partner Group Lotus.  The team achieved a race victory and fourth position in the Formula One Constructors' World Championship in their first season under the Lotus title.  The team was sold back to Renault on 18 December 2015, The Lotus F1 Team name was officially dropped on 3 February 2016, and announced that they would compete as Renault Sport Formula One Team.

Tom Belsø: Tom Belsø (born 27 August 1942 in Copenhagen, Denmark) is a former motor racing driver.  He is credited as the first Formula One driver from Denmark.  He started out in touring cars but became a Formula Two racer in 1972, with his best result being a fourth place at the Albi Grand Prix, finishing 17th in the European F2 Championship.  In 1973 he raced a Lola in Formula 5000.  He also raced in a few non-championship Formula One races, finishing 7th in the 1973 Race of Champions and 8th in the 1973 BRDC International Trophy, and retiring in the 1974 BRDC International Trophy and 1975 Race of Champions.  He contested the 1974 Rothmans 5000 European Championship winning at Snetterton and finishing 8th in the Series.  He also competed in the 1977 Shellsport 5000/Libre series and finished fifth in a Radio Luxemburg-sponsored Lola T330-Chevrolet.

1973 Dutch Grand Prix: The 1973 Dutch Grand Prix was a Formula One motor race held at Zandvoort on July 29, 1973.  It was race 10 of 15 in both the 1973 World Championship of Drivers and the 1973 International Cup for Formula One Manufacturers.  Zandvoort returned to the Formula One calendar following a year's absence for extensive safety upgrades to the race track including new asphalt, new barriers and a new race control tower.  Jackie Stewart won the race, this Grand Prix being fourth of five wins for Stewart during the 1973 Formula One season, and he became the most successful Formula One driver of all time with his 26th Grand Prix victory, surpassing Jim Clark's record of 25 victories.

Romain Grosjean: Romain Grosjean (] ; born 17 April 1986) is a racing driver, currently racing for the Haas F1 Team.  He races under the French flag in Formula One although he was born in Geneva and holds dual Franco-Swiss nationality.

Birabongse Bhanudej: Prince Birabongse Bhanudej Bhanubandh or Phra Chao Worawong Ther Phra Ong Chao Birabongse Bhunudej Thai: พระเจ้าวรวงศ์เธอ พระองค์เจ้าพีรพงศ์ภาณุเดช (born 15 July 191423 December 1985), better known as Prince Bira of Siam (now Thailand) or by his "nom de course" B. Bira, was the first and remains the only Thai to drive in Formula One.  He raced in Formula One and Grand Prix races for the Maserati, Gordini, and Connaught teams, among others.  He also was an Olympic sailor in the Melbourne Olympics, 1956 in the "Star", Rome Olympics, 1960 in the "Star", Tokyo Olympics, 1964 in the "Dragon" and the Munich Olympics, 1972 in the "Tempest".  In the 1960 Games he competed against another former Formula One driver, Roberto Mieres, who finished 17th, ahead of the prince at 19th.  Birabongse was the only Southeast Asian driver in Formula One until Malaysia's Alex Yoong joined Minardi in 2001.  Prince Bira was not only a racing driver, he was also a pilot of gliders and powered aircraft.  In 1952 he flew from London to Bangkok in his own twin engine Miles Gemini aircraft.

1965 Belgian Grand Prix: The 1965 Belgian Grand Prix was a Formula One motor race held at Spa-Francorchamps on 13 June 1965.  It was race 3 of 10 in both the 1965 World Championship of Drivers and the 1965 International Cup for Formula One Manufacturers.  The race was won by British driver Jim Clark who led every lap of the race driving a Lotus 33.  It was one of the Scot's most dominant wins.  In the rain, he pulled away and with a third of the race to go, the Lotus driver was leading his fellow Scotsman Jackie Stewart by 1 minute and 20 seconds.  However, for the last six laps Clark eased off dramatically and when the chequered flag was waved his lead was down to just under 45 seconds.

Colin Fleming (racing driver): Colin Fleming (born April 21, 1984 in San Diego, California) is an American former racing driver who completed in the Formula Renault 2.0 Eurocup, Formula Renault 2000 Germany and Formula Renault 3.5 in 2005 and 2006 with Jenzer Motorsport and Carlin Motorsport, he was also a member from the Red Bull Junior Team, Fleming finished 4th in the Formula Renault 2.0 Eurocup in 2004 and was rookie of the year in the Formula Renault 2000 Germany also in that year.  He also raced against fellow American and Californian and future Formula One Driver Scott Speed.  In 2005 he switched to the Formula Renault 3.5 with Swiss team Jenzer Motorsport, despite three DNS in the first 3 and missing one race of that season he finished 13th with 34 points with a best finish of 3rd in the second race in the Bugatti Circuit, to 2006 he switched to Carlin where he finished 6th in the first race of the season in Zolder, however he failed to qualify to the Second Race of the weekend and he finished 4th in Circuit de Monaco and 8th in both races in Istanbul Park, after this round he asked to leave Carlin and the Red Bull Junior Team, Red Bull officially released him and he was replaced by fellow Red Bull Junior Team member and Future Formula One Champion Sebastian Vettel, after leaving Red Bull, he returned to the United States to complete in the Atlantic Championship mid-season and he finished 20th with 45 points and since then has not raced anymore in a Major Series, until he decided to retire.  Now Colin is a high-level executive with Salesforce.

Supporting paragraphs: Lotus E23 Hybrid Romain Grosjean
Answer: the French flag